diff --git a/st.c b/st.c
index 816b3ec71d..2ce7a3fbee 100644
--- a/st.c
+++ b/st.c
@@ -2241,7 +2241,7 @@ rb_hash_bulk_insert(long argc, const VALUE *argv, VALUE hash)
 void
 Init_st(void)
 {
-    // initialize st_table pool
+    /* initialize st_table pool */
     list_head_init(&st_table_pool.head);
     st_table_pool.length = 0;
 }