diff --git a/tests/testthat/test-as_duckplyr_df.R b/tests/testthat/test-as_duckplyr_df.R
index d59b9fd7a..415d72ba6 100644
--- a/tests/testthat/test-as_duckplyr_df.R
+++ b/tests/testthat/test-as_duckplyr_df.R
@@ -1561,6 +1561,32 @@ test_that("as_duckplyr_df() and mutate(c = NA_character_, d = c %in% NA_characte
 })
 
 
+test_that("as_duckplyr_df() and mutate(d = a %in% NULL)", {
+  # Data
+  test_df <- data.frame(a = 1:6 + 0, b = 2, g = rep(1:3, 1:3))
+
+  # Run
+  pre <- test_df %>% as_duckplyr_df() %>% mutate(d = a %in% NULL)
+  post <- test_df %>% mutate(d = a %in% NULL) %>% as_duckplyr_df()
+
+  # Compare
+  expect_identical(pre, post)
+})
+
+
+test_that("as_duckplyr_df() and mutate(d = a %in% integer())", {
+  # Data
+  test_df <- data.frame(a = 1:6 + 0, b = 2, g = rep(1:3, 1:3))
+
+  # Run
+  pre <- test_df %>% as_duckplyr_df() %>% mutate(d = a %in% integer())
+  post <- test_df %>% mutate(d = a %in% integer()) %>% as_duckplyr_df()
+
+  # Compare
+  expect_identical(pre, post)
+})
+
+
 test_that("as_duckplyr_df() and mutate(d = NA_real_, e = is.na(d))", {
   # Data
   test_df <- data.frame(a = 1:6 + 0, b = 2, g = rep(1:3, 1:3))
@@ -1625,6 +1651,58 @@ test_that("as_duckplyr_df() and mutate(c = .data$b)", {
   expect_identical(pre, post)
 })
 
+
+test_that("as_duckplyr_df() and mutate(d = NA)", {
+  # Data
+  test_df <- data.frame(a = 1:6 + 0, b = 2, g = rep(1:3, 1:3))
+
+  # Run
+  pre <- test_df %>% as_duckplyr_df() %>% mutate(d = NA)
+  post <- test_df %>% mutate(d = NA) %>% as_duckplyr_df()
+
+  # Compare
+  expect_identical(pre, post)
+})
+
+
+test_that("as_duckplyr_df() and mutate(d = NA_integer_)", {
+  # Data
+  test_df <- data.frame(a = 1:6 + 0, b = 2, g = rep(1:3, 1:3))
+
+  # Run
+  pre <- test_df %>% as_duckplyr_df() %>% mutate(d = NA_integer_)
+  post <- test_df %>% mutate(d = NA_integer_) %>% as_duckplyr_df()
+
+  # Compare
+  expect_identical(pre, post)
+})
+
+
+test_that("as_duckplyr_df() and mutate(d = NA_real_)", {
+  # Data
+  test_df <- data.frame(a = 1:6 + 0, b = 2, g = rep(1:3, 1:3))
+
+  # Run
+  pre <- test_df %>% as_duckplyr_df() %>% mutate(d = NA_real_)
+  post <- test_df %>% mutate(d = NA_real_) %>% as_duckplyr_df()
+
+  # Compare
+  expect_identical(pre, post)
+})
+
+
+test_that("as_duckplyr_df() and mutate(d = NA_character_)", {
+  # Data
+  test_df <- data.frame(a = 1:6 + 0, b = 2, g = rep(1:3, 1:3))
+
+  # Run
+  pre <- test_df %>% as_duckplyr_df() %>% mutate(d = NA_character_)
+  post <- test_df %>% mutate(d = NA_character_) %>% as_duckplyr_df()
+
+  # Compare
+  expect_identical(pre, post)
+})
+
 test_that("as_duckplyr_df() and n_groups()", {
   withr::local_envvar(DUCKPLYR_FORCE = "FALSE")
 
diff --git a/tests/testthat/test-rel_api.R b/tests/testthat/test-rel_api.R
index 88c82a270..4f91f87cd 100644
--- a/tests/testthat/test-rel_api.R
+++ b/tests/testthat/test-rel_api.R
@@ -8712,6 +8712,110 @@ test_that("relational mutate(c = NA_character_, d = c %in% NA_character_) order-
   DBI::dbDisconnect(con, shutdown = TRUE)
 })
 
+test_that("relational mutate(d = a %in% NULL) order-preserving", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(FALSE, experimental = experimental)
+        } else {
+          duckdb$expr_constant(FALSE)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
+        tmp_expr
+      }
+    )
+  )
+  rel2
+  out <- duckdb$rel_to_altrep(rel2)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      d = logical(6)
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
+test_that("relational mutate(d = a %in% integer()) order-preserving", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(FALSE, experimental = experimental)
+        } else {
+          duckdb$expr_constant(FALSE)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
+        tmp_expr
+      }
+    )
+  )
+  rel2
+  out <- duckdb$rel_to_altrep(rel2)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      d = logical(6)
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
 test_that("relational mutate(d = NA_real_, e = is.na(d)) order-preserving", {
   # Autogenerated
   duckdb <- asNamespace("duckdb")
@@ -9087,31 +9191,56 @@ test_that("relational mutate(c = .data$b) order-preserving", {
   DBI::dbDisconnect(con, shutdown = TRUE)
 })
 
-# mutate order-enforcing ---------------------------------------------------------------
-
-test_that("relational mutate() order-enforcing", {
+test_that("relational mutate(d = NA) order-preserving", {
   # Autogenerated
   duckdb <- asNamespace("duckdb")
   drv <- duckdb::duckdb()
   con <- DBI::dbConnect(drv)
   experimental <- FALSE
+  invisible(DBI::dbExecute(con, 'CREATE MACRO "___null"() AS CAST(NULL AS BOOLEAN)'))
   df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
 
   rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
-  rel2 <- duckdb$rel_order(
+  rel2 <- duckdb$rel_project(
     rel1,
-    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"))
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_function("___null", list())
+        duckdb$expr_set_alias(tmp_expr, "d")
+        tmp_expr
+      }
+    )
   )
   rel2
   out <- duckdb$rel_to_altrep(rel2)
   expect_identical(
     out,
-    data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      d = rep(NA, 6L)
+    )
   )
   DBI::dbDisconnect(con, shutdown = TRUE)
 })
 
-test_that("relational mutate(a + 1) order-enforcing", {
+test_that("relational mutate(d = NA_integer_) order-preserving", {
   # Autogenerated
   duckdb <- asNamespace("duckdb")
   drv <- duckdb::duckdb()
@@ -9139,42 +9268,31 @@ test_that("relational mutate(a + 1) order-enforcing", {
         tmp_expr
       },
       {
-        tmp_expr <- duckdb$expr_function(
-          "+",
-          list(
-            duckdb$expr_reference("a"),
-            if ("experimental" %in% names(formals(duckdb$expr_constant))) {
-              duckdb$expr_constant(1, experimental = experimental)
-            } else {
-              duckdb$expr_constant(1)
-            }
-          )
-        )
-        duckdb$expr_set_alias(tmp_expr, "a + 1")
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(NA_integer_, experimental = experimental)
+        } else {
+          duckdb$expr_constant(NA_integer_)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
         tmp_expr
       }
     )
   )
-  rel3 <- duckdb$rel_order(
-    rel2,
-    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("a + 1"))
-  )
-  rel3
-  out <- duckdb$rel_to_altrep(rel3)
+  rel2
+  out <- duckdb$rel_to_altrep(rel2)
   expect_identical(
     out,
     data.frame(
       a = seq(1, 6, by = 1),
       b = rep(2, 6L),
       g = c(1L, 2L, 2L, 3L, 3L, 3L),
-      `a + 1` = seq(2, 7, by = 1),
-      check.names = FALSE
+      d = rep(NA_integer_, 6L)
     )
   )
   DBI::dbDisconnect(con, shutdown = TRUE)
 })
 
-test_that("relational mutate(a + 1, .by = g) order-enforcing", {
+test_that("relational mutate(d = NA_real_) order-preserving", {
   # Autogenerated
   duckdb <- asNamespace("duckdb")
   drv <- duckdb::duckdb()
@@ -9202,42 +9320,31 @@ test_that("relational mutate(a + 1, .by = g) order-enforcing", {
         tmp_expr
       },
       {
-        tmp_expr <- duckdb$expr_function(
-          "+",
-          list(
-            duckdb$expr_reference("a"),
-            if ("experimental" %in% names(formals(duckdb$expr_constant))) {
-              duckdb$expr_constant(1, experimental = experimental)
-            } else {
-              duckdb$expr_constant(1)
-            }
-          )
-        )
-        duckdb$expr_set_alias(tmp_expr, "a + 1")
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(NA_real_, experimental = experimental)
+        } else {
+          duckdb$expr_constant(NA_real_)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
         tmp_expr
       }
     )
   )
-  rel3 <- duckdb$rel_order(
-    rel2,
-    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("a + 1"))
-  )
-  rel3
-  out <- duckdb$rel_to_altrep(rel3)
+  rel2
+  out <- duckdb$rel_to_altrep(rel2)
   expect_identical(
     out,
     data.frame(
       a = seq(1, 6, by = 1),
       b = rep(2, 6L),
       g = c(1L, 2L, 2L, 3L, 3L, 3L),
-      `a + 1` = seq(2, 7, by = 1),
-      check.names = FALSE
+      d = rep(NA_real_, 6L)
     )
   )
   DBI::dbDisconnect(con, shutdown = TRUE)
 })
 
-test_that("relational mutate(c = a + 1) order-enforcing", {
+test_that("relational mutate(d = NA_character_) order-preserving", {
   # Autogenerated
   duckdb <- asNamespace("duckdb")
   drv <- duckdb::duckdb()
@@ -9265,41 +9372,55 @@ test_that("relational mutate(c = a + 1) order-enforcing", {
         tmp_expr
       },
       {
-        tmp_expr <- duckdb$expr_function(
-          "+",
-          list(
-            duckdb$expr_reference("a"),
-            if ("experimental" %in% names(formals(duckdb$expr_constant))) {
-              duckdb$expr_constant(1, experimental = experimental)
-            } else {
-              duckdb$expr_constant(1)
-            }
-          )
-        )
-        duckdb$expr_set_alias(tmp_expr, "c")
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(NA_character_, experimental = experimental)
+        } else {
+          duckdb$expr_constant(NA_character_)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
         tmp_expr
       }
     )
   )
-  rel3 <- duckdb$rel_order(
-    rel2,
-    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("c"))
-  )
-  rel3
-  out <- duckdb$rel_to_altrep(rel3)
+  rel2
+  out <- duckdb$rel_to_altrep(rel2)
   expect_identical(
     out,
     data.frame(
       a = seq(1, 6, by = 1),
       b = rep(2, 6L),
       g = c(1L, 2L, 2L, 3L, 3L, 3L),
-      c = seq(2, 7, by = 1)
+      d = rep(NA_character_, 6L)
     )
   )
   DBI::dbDisconnect(con, shutdown = TRUE)
 })
 
-test_that("relational mutate(`if` = a + 1) order-enforcing", {
+# mutate order-enforcing ---------------------------------------------------------------
+
+test_that("relational mutate() order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_order(
+    rel1,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"))
+  )
+  rel2
+  out <- duckdb$rel_to_altrep(rel2)
+  expect_identical(
+    out,
+    data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
+test_that("relational mutate(a + 1) order-enforcing", {
   # Autogenerated
   duckdb <- asNamespace("duckdb")
   drv <- duckdb::duckdb()
@@ -9338,14 +9459,14 @@ test_that("relational mutate(`if` = a + 1) order-enforcing", {
             }
           )
         )
-        duckdb$expr_set_alias(tmp_expr, "if")
+        duckdb$expr_set_alias(tmp_expr, "a + 1")
         tmp_expr
       }
     )
   )
   rel3 <- duckdb$rel_order(
     rel2,
-    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("if"))
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("a + 1"))
   )
   rel3
   out <- duckdb$rel_to_altrep(rel3)
@@ -9355,14 +9476,14 @@ test_that("relational mutate(`if` = a + 1) order-enforcing", {
       a = seq(1, 6, by = 1),
       b = rep(2, 6L),
       g = c(1L, 2L, 2L, 3L, 3L, 3L),
-      `if` = seq(2, 7, by = 1),
+      `a + 1` = seq(2, 7, by = 1),
       check.names = FALSE
     )
   )
   DBI::dbDisconnect(con, shutdown = TRUE)
 })
 
-test_that("relational mutate(sum(a)) order-enforcing", {
+test_that("relational mutate(a + 1, .by = g) order-enforcing", {
   # Autogenerated
   duckdb <- asNamespace("duckdb")
   drv <- duckdb::duckdb()
@@ -9390,11 +9511,199 @@ test_that("relational mutate(sum(a)) order-enforcing", {
         tmp_expr
       },
       {
-        tmp_expr <- duckdb$expr_window(duckdb$expr_function("sum", list(duckdb$expr_reference("a"))), list(), list(), offset_expr = NULL, default_expr = NULL)
-        duckdb$expr_set_alias(tmp_expr, "sum(a)")
-        tmp_expr
-      }
-    )
+        tmp_expr <- duckdb$expr_function(
+          "+",
+          list(
+            duckdb$expr_reference("a"),
+            if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+              duckdb$expr_constant(1, experimental = experimental)
+            } else {
+              duckdb$expr_constant(1)
+            }
+          )
+        )
+        duckdb$expr_set_alias(tmp_expr, "a + 1")
+        tmp_expr
+      }
+    )
+  )
+  rel3 <- duckdb$rel_order(
+    rel2,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("a + 1"))
+  )
+  rel3
+  out <- duckdb$rel_to_altrep(rel3)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      `a + 1` = seq(2, 7, by = 1),
+      check.names = FALSE
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
+test_that("relational mutate(c = a + 1) order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_function(
+          "+",
+          list(
+            duckdb$expr_reference("a"),
+            if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+              duckdb$expr_constant(1, experimental = experimental)
+            } else {
+              duckdb$expr_constant(1)
+            }
+          )
+        )
+        duckdb$expr_set_alias(tmp_expr, "c")
+        tmp_expr
+      }
+    )
+  )
+  rel3 <- duckdb$rel_order(
+    rel2,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("c"))
+  )
+  rel3
+  out <- duckdb$rel_to_altrep(rel3)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      c = seq(2, 7, by = 1)
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
+test_that("relational mutate(`if` = a + 1) order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_function(
+          "+",
+          list(
+            duckdb$expr_reference("a"),
+            if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+              duckdb$expr_constant(1, experimental = experimental)
+            } else {
+              duckdb$expr_constant(1)
+            }
+          )
+        )
+        duckdb$expr_set_alias(tmp_expr, "if")
+        tmp_expr
+      }
+    )
+  )
+  rel3 <- duckdb$rel_order(
+    rel2,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("if"))
+  )
+  rel3
+  out <- duckdb$rel_to_altrep(rel3)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      `if` = seq(2, 7, by = 1),
+      check.names = FALSE
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
+test_that("relational mutate(sum(a)) order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_window(duckdb$expr_function("sum", list(duckdb$expr_reference("a"))), list(), list(), offset_expr = NULL, default_expr = NULL)
+        duckdb$expr_set_alias(tmp_expr, "sum(a)")
+        tmp_expr
+      }
+    )
   )
   rel3 <- duckdb$rel_order(
     rel2,
@@ -12338,6 +12647,118 @@ test_that("relational mutate(c = NA_character_, d = c %in% NA_character_) order-
   DBI::dbDisconnect(con, shutdown = TRUE)
 })
 
+test_that("relational mutate(d = a %in% NULL) order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(FALSE, experimental = experimental)
+        } else {
+          duckdb$expr_constant(FALSE)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
+        tmp_expr
+      }
+    )
+  )
+  rel3 <- duckdb$rel_order(
+    rel2,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("d"))
+  )
+  rel3
+  out <- duckdb$rel_to_altrep(rel3)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      d = logical(6)
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
+test_that("relational mutate(d = a %in% integer()) order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(FALSE, experimental = experimental)
+        } else {
+          duckdb$expr_constant(FALSE)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
+        tmp_expr
+      }
+    )
+  )
+  rel3 <- duckdb$rel_order(
+    rel2,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("d"))
+  )
+  rel3
+  out <- duckdb$rel_to_altrep(rel3)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      d = logical(6)
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
 test_that("relational mutate(d = NA_real_, e = is.na(d)) order-enforcing", {
   # Autogenerated
   duckdb <- asNamespace("duckdb")
@@ -12677,6 +13098,227 @@ test_that("relational mutate(c = .data$b) order-enforcing", {
   DBI::dbDisconnect(con, shutdown = TRUE)
 })
 
+test_that("relational mutate(d = NA) order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  invisible(DBI::dbExecute(con, 'CREATE MACRO "___null"() AS CAST(NULL AS BOOLEAN)'))
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_function("___null", list())
+        duckdb$expr_set_alias(tmp_expr, "d")
+        tmp_expr
+      }
+    )
+  )
+  rel3 <- duckdb$rel_order(
+    rel2,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("d"))
+  )
+  rel3
+  out <- duckdb$rel_to_altrep(rel3)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      d = rep(NA, 6L)
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
+test_that("relational mutate(d = NA_integer_) order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(NA_integer_, experimental = experimental)
+        } else {
+          duckdb$expr_constant(NA_integer_)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
+        tmp_expr
+      }
+    )
+  )
+  rel3 <- duckdb$rel_order(
+    rel2,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("d"))
+  )
+  rel3
+  out <- duckdb$rel_to_altrep(rel3)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      d = rep(NA_integer_, 6L)
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
+test_that("relational mutate(d = NA_real_) order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(NA_real_, experimental = experimental)
+        } else {
+          duckdb$expr_constant(NA_real_)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
+        tmp_expr
+      }
+    )
+  )
+  rel3 <- duckdb$rel_order(
+    rel2,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("d"))
+  )
+  rel3
+  out <- duckdb$rel_to_altrep(rel3)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      d = rep(NA_real_, 6L)
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
+test_that("relational mutate(d = NA_character_) order-enforcing", {
+  # Autogenerated
+  duckdb <- asNamespace("duckdb")
+  drv <- duckdb::duckdb()
+  con <- DBI::dbConnect(drv)
+  experimental <- FALSE
+  df1 <- data.frame(a = seq(1, 6, by = 1), b = rep(2, 6L), g = c(1L, 2L, 2L, 3L, 3L, 3L))
+
+  rel1 <- duckdb$rel_from_df(con, df1, experimental = experimental)
+  rel2 <- duckdb$rel_project(
+    rel1,
+    list(
+      {
+        tmp_expr <- duckdb$expr_reference("a")
+        duckdb$expr_set_alias(tmp_expr, "a")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("b")
+        duckdb$expr_set_alias(tmp_expr, "b")
+        tmp_expr
+      },
+      {
+        tmp_expr <- duckdb$expr_reference("g")
+        duckdb$expr_set_alias(tmp_expr, "g")
+        tmp_expr
+      },
+      {
+        tmp_expr <- if ("experimental" %in% names(formals(duckdb$expr_constant))) {
+          duckdb$expr_constant(NA_character_, experimental = experimental)
+        } else {
+          duckdb$expr_constant(NA_character_)
+        }
+        duckdb$expr_set_alias(tmp_expr, "d")
+        tmp_expr
+      }
+    )
+  )
+  rel3 <- duckdb$rel_order(
+    rel2,
+    list(duckdb$expr_reference("a"), duckdb$expr_reference("b"), duckdb$expr_reference("g"), duckdb$expr_reference("d"))
+  )
+  rel3
+  out <- duckdb$rel_to_altrep(rel3)
+  expect_identical(
+    out,
+    data.frame(
+      a = seq(1, 6, by = 1),
+      b = rep(2, 6L),
+      g = c(1L, 2L, 2L, 3L, 3L, 3L),
+      d = rep(NA_character_, 6L)
+    )
+  )
+  DBI::dbDisconnect(con, shutdown = TRUE)
+})
+
 # relocate order-preserving ------------------------------------------------------------
 
 test_that("relational relocate(g) order-preserving", {
diff --git a/tools/00-funs.R b/tools/00-funs.R
index 5c22b3d95..dd35a9c47 100644
--- a/tools/00-funs.R
+++ b/tools/00-funs.R
@@ -646,6 +646,10 @@ test_extra_arg_map <- list(
     "d = a %in% NA_real_",
     "c = NA_character_, d = c %in% NA_character_",
 
+    # %in% and empty
+    "d = a %in% NULL",
+    "d = a %in% integer()",
+
     # is.na() with NaN
     "d = NA_real_, e = is.na(d)",
     "d = NaN, e = is.na(d)",
@@ -657,6 +661,12 @@ test_extra_arg_map <- list(
     # .data adverb
     "c = .data$b",
 
+    # NA constant
+    "d = NA",
+    "d = NA_integer_",
+    "d = NA_real_",
+    "d = NA_character_",
+
     NULL
   ),
   nest_join = "join_by(a)",