Index: backend/kvs40xx.h
--- backend/kvs40xx.h.orig
+++ backend/kvs40xx.h
@@ -9,6 +9,7 @@
 */
 
 #include "../include/sane/config.h"
+#include <pthread.h>
 #include <semaphore.h>
 #ifdef HAVE_SYS_TYPES_H
 #include <sys/types.h>