1 files changed, 4 insertions, 1 deletions
diff --git a/id.h b/id.h
index 3ea63db70d..15654b2be3 100644
--- a/id.h
+++ b/id.h
@@ -9,6 +9,9 @@
 
 **********************************************************************/
 
+#ifndef RUBY_ID_H
+#define RUBY_ID_H
+
 extern VALUE symIFUNC;
 extern VALUE symCFUNC;
 
@@ -48,4 +51,4 @@ extern ID idAnswer;
 extern ID idSend;
 extern ID id__send__;
 
-
+#endif /* RUBY_ID_H */