diff --git a/cty/type.go b/cty/type.go
index 4406908..fef1cfe 100644
--- a/cty/type.go
+++ b/cty/type.go
@@ -120,7 +120,7 @@ func (t Type) HasDynamicTypes() bool {
 // object types. This operation is applied recursively.
 func (t Type) WithoutOptionalAttributesDeep() Type {
 	switch {
-	case t == DynamicPseudoType, t.IsPrimitiveType(), t.IsCapsuleType():
+	case t == DynamicPseudoType, t == NilType, t.IsPrimitiveType(), t.IsCapsuleType():
 		return t
 	case t.IsMapType():
 		return Map(t.ElementType().WithoutOptionalAttributesDeep())
diff --git a/cty/type_test.go b/cty/type_test.go
index f5445a8..224d5d2 100644
--- a/cty/type_test.go
+++ b/cty/type_test.go
@@ -64,6 +64,10 @@ func TestWithoutOptionalAttributesDeep(t *testing.T) {
 			DynamicPseudoType,
 			DynamicPseudoType,
 		},
+		{
+			NilType,
+			NilType,
+		},
 		{
 			List(DynamicPseudoType),
 			List(DynamicPseudoType),