diff -r d2bbf907a189 -r 3b985a4eb05b src/ucx/ucx.h
--- a/src/ucx/ucx.h	Fri Sep 28 21:47:30 2018 +0200
+++ b/src/ucx/ucx.h	Sun Oct 07 09:00:08 2018 +0200
@@ -133,7 +133,7 @@
 
 
 
-#if defined(__GNUC__) || defined(__clang__)
+#if __GNUC__ >= 5 || defined(__clang__)
 #define UCX_MUL_BUILTIN
 
 #if __WORDSIZE == 32
@@ -181,7 +181,9 @@
  * @return zero, if no overflow occurred and the result is correct, non-zero
  * otherwise
  */
-int ucx_szmul(size_t a, size_t b, size_t *result);
+#define ucx_szmul(a, b, result) ucx_szmul_impl(a, b, result)
+
+int ucx_szmul_impl(size_t a, size_t b, size_t *result);
 
 #endif