Index: src/Common/utility.h
===================================================================
--- src/Common/utility.h	(revision a1f706482c1b8c9f3c9d9423a114c34f73c401e3)
+++ src/Common/utility.h	(revision 3c09d47c9fd762e66a4beaa4d096faba191e8d2a)
@@ -311,5 +311,5 @@
 struct group_iterate_t {
 	group_iterate_t( bool skipBoundsCheck, const T1 & v1, const T2 & v2 ) : args(v1, v2) {
-		assertf(skipBoundsCheck || v1.size() == v2.size(), "group iteration requires containers of the same size: <%lu, %lu>.", v1.size(), v2.size());
+		assertf(skipBoundsCheck || v1.size() == v2.size(), "group iteration requires containers of the same size: <%zd, %zd>.", v1.size(), v2.size());
 	};