diff --git a/clippy_lints/src/missing_asserts_for_indexing.rs b/clippy_lints/src/missing_asserts_for_indexing.rs
index ff2792faf57a..5d6dc8d5582c 100644
--- a/clippy_lints/src/missing_asserts_for_indexing.rs
+++ b/clippy_lints/src/missing_asserts_for_indexing.rs
@@ -9,7 +9,7 @@ use clippy_utils::{eq_expr_value, hash_expr, higher};
 use rustc_ast::{LitKind, RangeLimits};
 use rustc_data_structures::unhash::UnhashMap;
 use rustc_errors::{Applicability, Diagnostic};
-use rustc_hir::{BinOp, Block, Expr, ExprKind, UnOp};
+use rustc_hir::{BinOp, Block, Body, Expr, ExprKind, UnOp};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::source_map::Spanned;
@@ -390,10 +390,10 @@ fn report_indexes(cx: &LateContext<'_>, map: &UnhashMap<u64, Vec<IndexEntry<'_>>
 }
 
 impl LateLintPass<'_> for MissingAssertsForIndexing {
-    fn check_block(&mut self, cx: &LateContext<'_>, block: &Block<'_>) {
+    fn check_body(&mut self, cx: &LateContext<'_>, body: &Body<'_>) {
         let mut map = UnhashMap::default();
 
-        for_each_expr(block, |expr| {
+        for_each_expr(body.value, |expr| {
             check_index(cx, expr, &mut map);
             check_assert(cx, expr, &mut map);
             ControlFlow::<!, ()>::Continue(())
diff --git a/tests/ui/missing_asserts_for_indexing_unfixable.rs b/tests/ui/missing_asserts_for_indexing_unfixable.rs
index 4346ed892f27..de53079a4760 100644
--- a/tests/ui/missing_asserts_for_indexing_unfixable.rs
+++ b/tests/ui/missing_asserts_for_indexing_unfixable.rs
@@ -46,4 +46,26 @@ fn index_struct_different_fields(f: &Foo<'_>) {
     let _ = f.v[0] + f.v2[1];
 }
 
+fn shadowing() {
+    let x: &[i32] = &[1];
+    assert!(x.len() > 1);
+
+    let x: &[i32] = &[1];
+    let _ = x[0] + x[1];
+    //~^ ERROR: indexing into a slice multiple times without an `assert`
+}
+
+pub fn issue11856(values: &[i32]) -> usize {
+    let mut ascending = Vec::new();
+    for w in values.windows(2) {
+        assert!(w.len() > 1);
+        if w[0] < w[1] {
+            ascending.push((w[0], w[1]));
+        } else {
+            ascending.push((w[1], w[0]));
+        }
+    }
+    ascending.len()
+}
+
 fn main() {}
diff --git a/tests/ui/missing_asserts_for_indexing_unfixable.stderr b/tests/ui/missing_asserts_for_indexing_unfixable.stderr
index 12c9eed5d661..12e054227983 100644
--- a/tests/ui/missing_asserts_for_indexing_unfixable.stderr
+++ b/tests/ui/missing_asserts_for_indexing_unfixable.stderr
@@ -160,5 +160,24 @@ LL |     let _ = f.v[0] + f.v[1];
    |                      ^^^^^^
    = note: asserting the length before indexing will elide bounds checks
 
-error: aborting due to 7 previous errors
+error: indexing into a slice multiple times without an `assert`
+  --> $DIR/missing_asserts_for_indexing_unfixable.rs:54:13
+   |
+LL |     let _ = x[0] + x[1];
+   |             ^^^^^^^^^^^
+   |
+   = help: consider asserting the length before indexing: `assert!(x.len() > 1);`
+note: slice indexed here
+  --> $DIR/missing_asserts_for_indexing_unfixable.rs:54:13
+   |
+LL |     let _ = x[0] + x[1];
+   |             ^^^^
+note: slice indexed here
+  --> $DIR/missing_asserts_for_indexing_unfixable.rs:54:20
+   |
+LL |     let _ = x[0] + x[1];
+   |                    ^^^^
+   = note: asserting the length before indexing will elide bounds checks
+
+error: aborting due to 8 previous errors