diff --git a/git-compat-util.h b/git-compat-util.h
index 93f558056d..3bcf5b13f2 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -91,6 +91,9 @@ static inline void *xmalloc(size_t size)
 		ret = malloc(1);
 	if (!ret)
 		die("Out of memory, malloc failed");
+#ifdef XMALLOC_POISON
+	memset(ret, 0xA5, size);
+#endif
 	return ret;
 }