diff --git a/lib/libohash/ohash.h b/lib/libohash/ohash.h
index 03de431d726b..ff21c8599ead 100644
--- a/lib/libohash/ohash.h
+++ b/lib/libohash/ohash.h
@@ -20,6 +20,8 @@
 #ifndef OHASH_H
 #define OHASH_H
 
+#include <stddef.h>
+
 /* Open hashing support. 
  * Open hashing was chosen because it is much lighter than other hash
  * techniques, and more efficient in most cases.