diff --git a/fdrs_types.h b/fdrs_types.h
index 13dd188..d3aa314 100644
--- a/fdrs_types.h
+++ b/fdrs_types.h
@@ -1,4 +1,5 @@
 #ifndef __FDRS_TYPES_H__
+#define __FDRS_TYPES_H__
 
 #include <stdint.h>