diff --git a/crates/red_knot_python_semantic/resources/mdtest/annotations/annotated.md b/crates/red_knot_python_semantic/resources/mdtest/annotations/annotated.md
index d16f496cc5f7b..71b06a24f280b 100644
--- a/crates/red_knot_python_semantic/resources/mdtest/annotations/annotated.md
+++ b/crates/red_knot_python_semantic/resources/mdtest/annotations/annotated.md
@@ -43,6 +43,10 @@ def _(flag: bool):
     def f(y: X):
         reveal_type(y)  # revealed: Unknown | bool
 
+# error: [invalid-type-form] "`Annotated` requires at least two arguments when used in an annotation or type expression"
+def _(x: Annotated | bool):
+    reveal_type(x)  # revealed: Unknown | bool
+
 # error: [invalid-type-form]
 def _(x: Annotated[()]):
     reveal_type(x)  # revealed: Unknown
diff --git a/crates/red_knot_python_semantic/src/types.rs b/crates/red_knot_python_semantic/src/types.rs
index 90de636acbfd1..580ebf5f3540d 100644
--- a/crates/red_knot_python_semantic/src/types.rs
+++ b/crates/red_knot_python_semantic/src/types.rs
@@ -28,7 +28,7 @@ use crate::stdlib::{
 use crate::symbol::{Boundness, Symbol};
 use crate::types::call::{CallDunderResult, CallOutcome};
 use crate::types::class_base::ClassBase;
-use crate::types::diagnostic::TypeCheckDiagnosticsBuilder;
+use crate::types::diagnostic::{TypeCheckDiagnosticsBuilder, INVALID_TYPE_FORM};
 use crate::types::mro::{Mro, MroError, MroIterator};
 use crate::types::narrow::narrowing_constraint;
 use crate::{Db, FxOrderSet, Module, Program, PythonVersion};
@@ -1889,7 +1889,7 @@ impl<'db> Type<'db> {
             Type::KnownInstance(KnownInstanceType::Tuple) => Ok(KnownClass::Tuple.to_instance(db)),
             Type::Union(union) => {
                 let mut builder = UnionBuilder::new(db);
-                let mut invalid_expressions = vec![];
+                let mut invalid_expressions = smallvec::SmallVec::default();
                 for element in union.elements(db) {
                     match element.in_type_expression(db) {
                         Ok(type_expr) => builder = builder.add(type_expr),
@@ -1922,11 +1922,11 @@ impl<'db> Type<'db> {
             Type::KnownInstance(KnownInstanceType::Any) => Ok(Type::Any),
             // TODO: Should emit a diagnostic
             Type::KnownInstance(KnownInstanceType::Annotated) => Err(InvalidTypeExpressionError {
-                invalid_expressions: vec![InvalidTypeExpression::BareAnnotated],
+                invalid_expressions: smallvec::smallvec![InvalidTypeExpression::BareAnnotated],
                 fallback_type: Type::Unknown,
             }),
             Type::KnownInstance(KnownInstanceType::Literal) => Err(InvalidTypeExpressionError {
-                invalid_expressions: vec![InvalidTypeExpression::BareLiteral],
+                invalid_expressions: smallvec::smallvec![InvalidTypeExpression::BareLiteral],
                 fallback_type: Type::Unknown,
             }),
             Type::Todo(_) => Ok(*self),
@@ -2067,7 +2067,28 @@ impl<'db> From<Type<'db>> for Symbol<'db> {
 #[derive(Debug, PartialEq, Eq)]
 pub struct InvalidTypeExpressionError<'db> {
     fallback_type: Type<'db>,
-    invalid_expressions: Vec<InvalidTypeExpression>,
+    invalid_expressions: smallvec::SmallVec<[InvalidTypeExpression; 1]>,
+}
+
+impl<'db> InvalidTypeExpressionError<'db> {
+    fn into_fallback_type(
+        self,
+        diagnostics: &mut TypeCheckDiagnosticsBuilder,
+        node: &ast::Expr,
+    ) -> Type<'db> {
+        let InvalidTypeExpressionError {
+            fallback_type,
+            invalid_expressions,
+        } = self;
+        for error in invalid_expressions {
+            diagnostics.add_lint(
+                &INVALID_TYPE_FORM,
+                node.into(),
+                format_args!("{}", error.reason()),
+            );
+        }
+        fallback_type
+    }
 }
 
 /// Enumeration of various types that are invalid in type-expression contexts
diff --git a/crates/red_knot_python_semantic/src/types/infer.rs b/crates/red_knot_python_semantic/src/types/infer.rs
index bed9247850129..d35b6c217366c 100644
--- a/crates/red_knot_python_semantic/src/types/infer.rs
+++ b/crates/red_knot_python_semantic/src/types/infer.rs
@@ -63,10 +63,10 @@ use crate::types::unpacker::{UnpackResult, Unpacker};
 use crate::types::{
     bindings_ty, builtins_symbol, declarations_ty, global_symbol, symbol, todo_type,
     typing_extensions_symbol, Boundness, Class, ClassLiteralType, FunctionType, InstanceType,
-    IntersectionBuilder, IntersectionType, InvalidTypeExpressionError, IterationOutcome,
-    KnownClass, KnownFunction, KnownInstanceType, MetaclassCandidate, MetaclassErrorKind,
-    SliceLiteralType, Symbol, Truthiness, TupleType, Type, TypeAliasType, TypeArrayDisplay,
-    TypeVarBoundOrConstraints, TypeVarInstance, UnionBuilder, UnionType,
+    IntersectionBuilder, IntersectionType, IterationOutcome, KnownClass, KnownFunction,
+    KnownInstanceType, MetaclassCandidate, MetaclassErrorKind, SliceLiteralType, Symbol,
+    Truthiness, TupleType, Type, TypeAliasType, TypeArrayDisplay, TypeVarBoundOrConstraints,
+    TypeVarInstance, UnionBuilder, UnionType,
 };
 use crate::unpack::Unpack;
 use crate::util::subscript::{PyIndex, PySlice};
@@ -4468,7 +4468,9 @@ impl<'db> TypeInferenceBuilder<'db> {
                 ast::ExprContext::Load => self
                     .infer_name_expression(name)
                     .in_type_expression(self.db)
-                    .unwrap_or_else(|error| self.infer_invalid_type_expression(expression, error)),
+                    .unwrap_or_else(|error| {
+                        error.into_fallback_type(&mut self.diagnostics, expression)
+                    }),
                 ast::ExprContext::Invalid => Type::Unknown,
                 ast::ExprContext::Store | ast::ExprContext::Del => todo_type!(),
             },
@@ -4477,7 +4479,9 @@ impl<'db> TypeInferenceBuilder<'db> {
                 ast::ExprContext::Load => self
                     .infer_attribute_expression(attribute_expression)
                     .in_type_expression(self.db)
-                    .unwrap_or_else(|error| self.infer_invalid_type_expression(expression, error)),
+                    .unwrap_or_else(|error| {
+                        error.into_fallback_type(&mut self.diagnostics, expression)
+                    }),
                 ast::ExprContext::Invalid => Type::Unknown,
                 ast::ExprContext::Store | ast::ExprContext::Del => todo_type!(),
             },
@@ -4633,25 +4637,6 @@ impl<'db> TypeInferenceBuilder<'db> {
         }
     }
 
-    fn infer_invalid_type_expression(
-        &mut self,
-        expression: &ast::Expr,
-        error: InvalidTypeExpressionError<'db>,
-    ) -> Type<'db> {
-        let InvalidTypeExpressionError {
-            fallback_type,
-            invalid_expressions,
-        } = error;
-        for error in invalid_expressions {
-            self.diagnostics.add_lint(
-                &INVALID_TYPE_FORM,
-                expression.into(),
-                format_args!("{}", error.reason()),
-            );
-        }
-        fallback_type
-    }
-
     /// Infer the type of a string type expression.
     fn infer_string_type_expression(&mut self, string: &ast::ExprStringLiteral) -> Type<'db> {
         match parse_string_annotation(self.db, self.file, string) {