diff --git a/lib/memory_mosq.c b/lib/memory_mosq.c
index b1f5bfd..4d8217d 100644
--- a/lib/memory_mosq.c
+++ b/lib/memory_mosq.c
@@ -54,6 +54,9 @@ void *mosquitto__calloc(size_t nmemb, size_t size)
 void mosquitto__free(void *mem)
 {
 #ifdef REAL_WITH_MEMORY_TRACKING
+	if(!mem){
+		return;
+	}
 	memcount -= malloc_usable_size(mem);
 #endif
 	free(mem);