diff --git a/tests/server/tftpd.c b/tests/server/tftpd.c
index cf85623af2a86acd4e6514479baf18284c910e30..e4fc8368327ab10d7ae6146a45360e2bc51aa6c4 100644
--- a/tests/server/tftpd.c
+++ b/tests/server/tftpd.c
@@ -228,7 +228,7 @@ static void read_ahead(struct testcase *test,
     /* decrease amount, advance pointer */
     test->rcount -= copy_n;
     test->rptr += copy_n;
-    b->counter = copy_n;
+    b->counter = (int)copy_n;
     return;
   }