Index: src/Common/utility.h
===================================================================
--- src/Common/utility.h	(revision 8135d4c79504a6c3047246007261186efa5ba4c9)
+++ src/Common/utility.h	(revision 1ae39f6ef81b096e92a97cbb3424c6cd48b4414b)
@@ -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());
 	};