diff --git a/ext/standard/dir.c b/ext/standard/dir.c
index 65f3f7d5533..4e8680d39a8 100644
--- a/ext/standard/dir.c
+++ b/ext/standard/dir.c
@@ -141,7 +141,7 @@ PHP_MINIT_FUNCTION(dir)
 #endif
     tmpstr[0] = DEFAULT_SLASH;
     tmpstr[1] = '\0';
-    REGISTER_STRING_CONSTANT("DIRECTORY_SEPARATOR", tmpstr, 0);
+    REGISTER_STRING_CONSTANT("DIRECTORY_SEPARATOR", tmpstr, CONST_PERSISTENT);
 
 	return SUCCESS;
 }