diff --git a/crates/red_knot_python_semantic/resources/mdtest/assignment/augmented.md b/crates/red_knot_python_semantic/resources/mdtest/assignment/augmented.md
index 65dfcef23ad52..316d5bdfdab4a 100644
--- a/crates/red_knot_python_semantic/resources/mdtest/assignment/augmented.md
+++ b/crates/red_knot_python_semantic/resources/mdtest/assignment/augmented.md
@@ -18,6 +18,14 @@ class C:
 x = C()
 x -= 1
 reveal_type(x)  # revealed: str
+
+class C:
+    def __iadd__(self, other: str) -> float:
+        return "Hello, world!"
+
+x = C()
+x += "Hello"
+reveal_type(x)  # revealed: float
 ```
 
 ## Unsupported types
diff --git a/crates/red_knot_python_semantic/src/types/infer.rs b/crates/red_knot_python_semantic/src/types/infer.rs
index 5080bd27c45f7..e6ed20fb5be0d 100644
--- a/crates/red_knot_python_semantic/src/types/infer.rs
+++ b/crates/red_knot_python_semantic/src/types/infer.rs
@@ -33,7 +33,7 @@ use itertools::Itertools;
 use ruff_db::files::File;
 use ruff_db::parsed::parsed_module;
 use ruff_python_ast::name::Name;
-use ruff_python_ast::{self as ast, AnyNodeRef, Expr, ExprContext, Operator, UnaryOp};
+use ruff_python_ast::{self as ast, AnyNodeRef, Expr, ExprContext, UnaryOp};
 use ruff_text_size::Ranged;
 use rustc_hash::FxHashMap;
 use salsa;
@@ -1425,10 +1425,9 @@ impl<'db> TypeInferenceBuilder<'db> {
         };
         let value_type = self.infer_expression(value);
 
-        // TODO(charlie): Add remaining branches for different types of augmented assignments.
-        if let (Operator::Sub, Type::Instance(class)) = (*op, target_type) {
-            let class_member = class.class_member(self.db, "__isub__");
-            let call = class_member.call(self.db, &[value_type]);
+        if let Type::Instance(class) = target_type {
+            let class_member = class.class_member(self.db, op.in_place_dunder());
+            let call = class_member.call(self.db, &[target_type, value_type]);
 
             return match call.return_ty_result(self.db, AnyNodeRef::StmtAugAssign(assignment), self)
             {
@@ -2516,9 +2515,7 @@ impl<'db> TypeInferenceBuilder<'db> {
         } = attribute;
 
         let value_ty = self.infer_expression(value);
-        let member_ty = value_ty.member(self.db, &Name::new(&attr.id));
-
-        member_ty
+        value_ty.member(self.db, &Name::new(&attr.id))
     }
 
     fn infer_attribute_expression(&mut self, attribute: &ast::ExprAttribute) -> Type<'db> {
diff --git a/crates/ruff_benchmark/benches/red_knot.rs b/crates/ruff_benchmark/benches/red_knot.rs
index 6e52ccc409965..b059df6af7b6e 100644
--- a/crates/ruff_benchmark/benches/red_knot.rs
+++ b/crates/ruff_benchmark/benches/red_knot.rs
@@ -28,22 +28,30 @@ static EXPECTED_DIAGNOSTICS: &[&str] = &[
     // We don't support terminal statements in control flow yet:
     "/src/tomllib/_parser.py:66:18: Name `s` used when possibly not defined",
     "/src/tomllib/_parser.py:98:12: Name `char` used when possibly not defined",
+    "/src/tomllib/_parser.py:99:13: Operator `+=` is unsupported for type `int` with type `Literal[1]`",
     "/src/tomllib/_parser.py:101:12: Name `char` used when possibly not defined",
     "/src/tomllib/_parser.py:104:14: Name `char` used when possibly not defined",
     "/src/tomllib/_parser.py:108:17: Conflicting declared types for `second_char`: Unknown, str | None",
     "/src/tomllib/_parser.py:115:14: Name `char` used when possibly not defined",
     "/src/tomllib/_parser.py:126:12: Name `char` used when possibly not defined",
+    "/src/tomllib/_parser.py:130:9: Operator `+=` is unsupported for type `int` with type `Literal[1]`",
     "/src/tomllib/_parser.py:267:9: Conflicting declared types for `char`: Unknown, str | None",
     "/src/tomllib/_parser.py:348:20: Name `nest` used when possibly not defined",
     "/src/tomllib/_parser.py:353:5: Name `nest` used when possibly not defined",
     "/src/tomllib/_parser.py:353:5: Method `__getitem__` of type `Unbound | @Todo` is not callable on object of type `Unbound | @Todo`",
     "/src/tomllib/_parser.py:364:9: Conflicting declared types for `char`: Unknown, str | None",
+    "/src/tomllib/_parser.py:367:5: Operator `+=` is unsupported for type `int` with type `Literal[1]`",
     "/src/tomllib/_parser.py:381:13: Conflicting declared types for `char`: Unknown, str | None",
+    "/src/tomllib/_parser.py:384:9: Operator `+=` is unsupported for type `int` with type `Literal[1]`",
     "/src/tomllib/_parser.py:395:9: Conflicting declared types for `char`: Unknown, str | None",
+    "/src/tomllib/_parser.py:429:9: Operator `+=` is unsupported for type `int` with type `Literal[1]`",
     "/src/tomllib/_parser.py:453:24: Name `nest` used when possibly not defined",
     "/src/tomllib/_parser.py:455:9: Name `nest` used when possibly not defined",
     "/src/tomllib/_parser.py:455:9: Method `__getitem__` of type `Unbound | @Todo` is not callable on object of type `Unbound | @Todo`",
+    "/src/tomllib/_parser.py:464:9: Operator `+=` is unsupported for type `int` with type `Literal[1]`",
     "/src/tomllib/_parser.py:482:16: Name `char` used when possibly not defined",
+    "/src/tomllib/_parser.py:484:13: Operator `+=` is unsupported for type `int` with type `Literal[1]`",
+    "/src/tomllib/_parser.py:545:5: Operator `+=` is unsupported for type `int` with type `Literal[1]`",
     "/src/tomllib/_parser.py:566:12: Name `char` used when possibly not defined",
     "/src/tomllib/_parser.py:573:12: Name `char` used when possibly not defined",
     "/src/tomllib/_parser.py:579:12: Name `char` used when possibly not defined",
diff --git a/crates/ruff_python_ast/src/nodes.rs b/crates/ruff_python_ast/src/nodes.rs
index a35868d6a0371..b0eb7f3e8a423 100644
--- a/crates/ruff_python_ast/src/nodes.rs
+++ b/crates/ruff_python_ast/src/nodes.rs
@@ -2972,6 +2972,7 @@ impl Operator {
         }
     }
 
+    /// Returns the dunder method name for the operator.
     pub const fn dunder(self) -> &'static str {
         match self {
             Operator::Add => "__add__",
@@ -2990,6 +2991,26 @@ impl Operator {
         }
     }
 
+    /// Returns the in-place dunder method name for the operator.
+    pub const fn in_place_dunder(self) -> &'static str {
+        match self {
+            Operator::Add => "__iadd__",
+            Operator::Sub => "__isub__",
+            Operator::Mult => "__imul__",
+            Operator::MatMult => "__imatmul__",
+            Operator::Div => "__itruediv__",
+            Operator::Mod => "__imod__",
+            Operator::Pow => "__ipow__",
+            Operator::LShift => "__ilshift__",
+            Operator::RShift => "__irshift__",
+            Operator::BitOr => "__ior__",
+            Operator::BitXor => "__ixor__",
+            Operator::BitAnd => "__iand__",
+            Operator::FloorDiv => "__ifloordiv__",
+        }
+    }
+
+    /// Returns the reflected dunder method name for the operator.
     pub const fn reflected_dunder(self) -> &'static str {
         match self {
             Operator::Add => "__radd__",