diff --git a/mingw-w64-tools/widl/src/typetree.h b/mingw-w64-tools/widl/src/typetree.h
index 8ba348b..180444d 100644
--- a/mingw-w64-tools/widl/src/typetree.h
+++ b/mingw-w64-tools/widl/src/typetree.h
@@ -115,7 +115,9 @@ static inline var_list_t *type_enum_get_values(const type_t *type)
 {
     type = type_get_real_type(type);
     assert(type_get_type(type) == TYPE_ENUM);
+    if (type->details.enumeration)
     return type->details.enumeration->enums;
+    return NULL;
 }

 static inline var_t *type_union_get_switch_value(const type_t *type)