diff --git a/src/diffarch.c b/src/diffarch.c
index de05ae6e..c4aaff87 100644
--- a/src/diffarch.c
+++ b/src/diffarch.c
@@ -38,7 +38,7 @@ extern int errno;
 #endif
 #endif
 
-#ifndef NO_MTIO
+#ifdef HAVE_SYS_MTIO_H
 #include <sys/ioctl.h>
 #include <sys/mtio.h>
 #endif