diff --git a/include/assert.h b/include/assert.h
index f621106..bcabb93 100644
--- a/include/assert.h
+++ b/include/assert.h
@@ -12,12 +12,13 @@
 #ifndef _ASSERT_H
 #define _ASSERT_H
 
+#include <stdlib.h>
 #include <stdio.h>
 
 #ifdef NDEBUG
 #define assert(ignore) ((void) 0)
 #else
-#define assert(expression) (expression || (fprintf(stderr, "%s: %d: %s", __FILE__, __LINE__, __func__) && abort()))
+#define assert(expression) (expression || (fprintf(stderr, "Assertion failed: %s: %d: %s", __FILE__, __LINE__, __func__) && abort()))
 #endif
 
 #endif