diff --git a/variable.c b/variable.c
index 1923f28f52..3e37bc2f72 100644
--- a/variable.c
+++ b/variable.c
@@ -22,7 +22,7 @@
 #include "id_table.h"
 #include "debug_counter.h"
 
-struct rb_id_table *rb_global_tbl;
+static struct rb_id_table *rb_global_tbl;
 static ID autoload, classpath, tmp_classpath, classid;
 
 static void check_before_mod_set(VALUE, ID, VALUE, const char *);