diff --git a/internal/fxreflect/stack_test.go b/internal/fxreflect/stack_test.go
index 400c7c2ba..c5eb8c949 100644
--- a/internal/fxreflect/stack_test.go
+++ b/internal/fxreflect/stack_test.go
@@ -47,25 +47,6 @@ func TestStack(t *testing.T) {
 		assert.NotZero(t, f.Line)
 	})
 
-	t.Run("default/deeper", func(t *testing.T) {
-		t.Parallel()
-
-		// Introduce a few frames.
-		frames := func() []Frame {
-			return func() []Frame {
-				return CallerStack(0, 0)
-			}()
-		}()
-
-		require.True(t, len(frames) > 3, "expected at least three frames")
-		for i, name := range []string{"func2.TestStack.func2.1.func2", "func2.1", "func2"} {
-			f := frames[i]
-			assert.Equal(t, "go.uber.org/fx/internal/fxreflect.TestStack."+name, f.Function)
-			assert.Contains(t, f.File, "internal/fxreflect/stack_test.go")
-			assert.NotZero(t, f.Line)
-		}
-	})
-
 	t.Run("skip", func(t *testing.T) {
 		t.Parallel()
 
@@ -78,7 +59,7 @@ func TestStack(t *testing.T) {
 
 		require.NotEmpty(t, frames)
 		f := frames[0]
-		assert.Equal(t, "go.uber.org/fx/internal/fxreflect.TestStack.func3", f.Function)
+		assert.Equal(t, "go.uber.org/fx/internal/fxreflect.TestStack.func2", f.Function)
 		assert.Contains(t, f.File, "internal/fxreflect/stack_test.go")
 		assert.NotZero(t, f.Line)
 	})
diff --git a/internal/fxreflect/stack_test_120.go b/internal/fxreflect/stack_test_120.go
new file mode 100644
index 000000000..b5e8e2f21
--- /dev/null
+++ b/internal/fxreflect/stack_test_120.go
@@ -0,0 +1,27 @@
+//go:build !go1.21
+// +build !go1.21
+
+package fxreflect
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDeepStack(t *testing.T) {
+	// Introduce a few frames.
+	frames := func() []Frame {
+		return func() []Frame {
+			return CallerStack(0, 0)
+		}()
+	}()
+
+	require.True(t, len(frames) > 3, "expected at least three frames")
+	for i, name := range []string{"func2.1.1", "func2.1", "func2"} {
+		f := frames[i]
+		assert.Equal(t, "go.uber.org/fx/internal/fxreflect.TestStack."+name, f.Function)
+		assert.Contains(t, f.File, "internal/fxreflect/stack_test.go")
+		assert.NotZero(t, f.Line)
+	}
+}
diff --git a/internal/fxreflect/stack_test_121.go b/internal/fxreflect/stack_test_121.go
new file mode 100644
index 000000000..40b03a2fe
--- /dev/null
+++ b/internal/fxreflect/stack_test_121.go
@@ -0,0 +1,28 @@
+//go:build go1.21
+// +build go1.21
+
+package fxreflect
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDeepStack(t *testing.T) {
+	// Introduce a few frames.
+	frames := func() []Frame {
+		return func() []Frame {
+			return CallerStack(0, 0)
+		}()
+	}()
+
+	require.True(t, len(frames) > 3, "expected at least three frames")
+	for i, name := range []string{"func2.TestStack.func2.1.func2", "func2.1", "func2"} {
+		f := frames[i]
+		assert.Equal(t, "go.uber.org/fx/internal/fxreflect.TestStack."+name, f.Function)
+		assert.Contains(t, f.File, "internal/fxreflect/stack_test.go")
+		assert.NotZero(t, f.Line)
+	}
+}