diff --git a/test/detail_iterator_test.cpp b/test/detail_iterator_test.cpp
index 5a4d484..a6ca7d7 100644
--- a/test/detail_iterator_test.cpp
+++ b/test/detail_iterator_test.cpp
@@ -30,9 +30,8 @@ using std::distance;
 
 */
 
-struct C
-{
-};
+// struct C {} doesn't wotk with libc++.
+typedef std::forward_iterator_tag C;
 
 struct T
 {