diff --git a/lib/isc/mem.c b/lib/isc/mem.c
index 120760ee23..704bfcca06 100644
--- a/lib/isc/mem.c
+++ b/lib/isc/mem.c
@@ -734,8 +734,8 @@ default_memalloc(void *arg, size_t size) {
 
 	if (ptr == NULL && size != 0) {
 		char strbuf[ISC_STRERRORSIZE];
-		strerror_r(errno, strbuf, sizeof(strbuf));
-		isc_error_fatal(__FILE__, __LINE__, "malloc failed: %s", strbuf);
+		isc_error_fatal(__FILE__, __LINE__, "malloc failed: %s",
+				strerror_r(errno, strbuf, sizeof(strbuf)));
 	}
 
 	return (ptr);