diff --git a/backend/microtek.c b/backend/microtek.c
index 200a69c1a..63560179c 100644
--- a/backend/microtek.c
+++ b/backend/microtek.c
@@ -57,6 +57,7 @@
 
 #include "../include/sane/config.h"
 
+#include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>