diff --git a/ext/io/wait/wait.c b/ext/io/wait/wait.c
index cf36346cf2..f7575191fe 100644
--- a/ext/io/wait/wait.c
+++ b/ext/io/wait/wait.c
@@ -17,8 +17,6 @@
  * IO wait methods are built in ruby now, just for backward compatibility.
  */
 
-#include "ruby.h"
-
 void
 Init_wait(void)
 {