diff --git a/str_lib.h b/str_lib.h
index d89a75b..6337b65 100644
--- a/str_lib.h
+++ b/str_lib.h
@@ -1,6 +1,7 @@
-#pragma once
+#ifndef STR_LIB_H
+#define STR_LIB_H
 
 int mystrlen(const char *s);
-
 int mystr_idx(const char *s1, const char *s2);
 
+#endif