--- backends/glass/glass_version.h
+++ backends/glass/glass_version.h
@@ -34,8 +34,9 @@
 #include "backends/uuids.h"
 #include "internaltypes.h"
 #include "min_non_zero.h"
 #include "xapian/types.h"
+#include <sys/types.h>
 
 namespace Glass {
 
 class RootInfo {