diff --git a/mjit.c b/mjit.c
index 4d0819153d..a4550e922c 100644
--- a/mjit.c
+++ b/mjit.c
@@ -469,7 +469,7 @@ init_header_filename(void)
     // Root path of the running ruby process. Equal to RbConfig::TOPDIR.
     VALUE basedir_val;
 #endif
-    const char *basedir = NULL;
+    const char *basedir = "";
     size_t baselen = 0;
     char *p;
 #ifdef _WIN32