diff --git a/lib/tftp.c b/lib/tftp.c
index 56b7afda52..8279f29e65 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -564,7 +564,7 @@ static CURLcode tftp_send_first(struct tftp_conn *state,
 
   default:
     failf(state->data, "tftp_send_first: internal error");
-    break;
+    return CURLE_TFTP_ILLEGAL;
   }
 
   return result;