Need to include <sys/types.h> for off_t.
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 09ea31c..ed15587 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -34,6 +34,8 @@
 #include "Python.h"
 #include "structmember.h"
 
+#include <sys/types.h>
+
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif