diff --git a/proptools/configurable.go b/proptools/configurable.go
index 4dfe007..55e4fb7 100644
--- a/proptools/configurable.go
+++ b/proptools/configurable.go
@@ -502,8 +502,12 @@ func (c *Configurable[T]) AddPostProcessor(p func(T) T) {
 	// See Configurable.evaluate for more details on the postProcessors algorithm
 	// and data structure.
 	num_links := c.inner.numLinks()
-	if c.postProcessors == nil || len(*c.postProcessors) == 0 {
-		c.postProcessors = &[][]postProcessor[T]{{{
+	if c.postProcessors == nil {
+		var nilCases []ConfigurableCase[T]
+		c.initialize(nil, "", nil, nilCases)
+	}
+	if len(*c.postProcessors) == 0 {
+		*c.postProcessors = [][]postProcessor[T]{{{
 			f:     p,
 			start: 0,
 			end:   num_links,
diff --git a/proptools/configurable_test.go b/proptools/configurable_test.go
index f3ea417..f608a45 100644
--- a/proptools/configurable_test.go
+++ b/proptools/configurable_test.go
@@ -43,6 +43,24 @@ func TestPostProcessor(t *testing.T) {
 	}
 }
 
+func TestPostProcessorWhenPassedToHelperFunction(t *testing.T) {
+	prop := NewConfigurable[[]string](nil, nil)
+	prop.AppendSimpleValue([]string{"a"})
+	prop.AppendSimpleValue([]string{"b"})
+
+	helper := func(p Configurable[[]string]) {
+		p.AddPostProcessor(addToElements("1"))
+	}
+
+	helper(prop)
+
+	expected := []string{"a1", "b1"}
+	x := prop.Get(&configurableEvalutorForTesting{})
+	if !reflect.DeepEqual(x.Get(), expected) {
+		t.Fatalf("Expected %v, got %v", expected, x.Get())
+	}
+}
+
 func addToElements(s string) func([]string) []string {
 	return func(arr []string) []string {
 		for i := range arr {