diff --git a/tools/bit/util.h b/tools/bit/util.h
index 7ccdab1..8c66911 100644
--- a/tools/bit/util.h
+++ b/tools/bit/util.h
@@ -17,6 +17,8 @@
 #ifndef UTIL_H
 #define UTIL_H
 
+#include <sys/types.h>
+
 #include <map>
 #include <string>
 #include <vector>