diff --git a/common.h b/common.h
index 4769102..237ced4 100644
--- a/common.h
+++ b/common.h
@@ -17,6 +17,9 @@
  *  function prototypes that are sometimes missing.
  */
 
+#ifndef __COMMON_H__
+#define __COMMON_H__
+
 /* C99 types */
 #if defined HAVE_INTTYPES_H && !defined __KERNEL__
 #   include <inttypes.h>
@@ -78,3 +81,5 @@ static inline uint32_t hton32(uint32_t x)
 }
 #endif
 
+#endif /* __COMMON_H__ */
+