diff --git a/rdwrops.h b/rdwrops.h
index d223cbb..11d8c60 100644
--- a/rdwrops.h
+++ b/rdwrops.h
@@ -6,6 +6,7 @@
 */
 
 #ifndef _RD_WR_OPS_H_
+#define _RD_WR_OPS_H_
 
 #include <string>
 #include <vector>