diff --git a/v4l2/grabvidseq.c b/v4l2/grabvidseq.c
index ef855ae..16b0acf 100644
--- a/v4l2/grabvidseq.c
+++ b/v4l2/grabvidseq.c
@@ -168,6 +168,11 @@ if (verbosity > 1) {
 	if (upscaling) fprintf(stderr, "upscaling is on\n");
 	}
 
+if (upscaling && (nbre_capt%4)) {
+	fprintf(stderr, "WARN upscaling: %d bad nbre_capt\n",
+					   nbre_capt);
+	}
+
 fd = v4l2_open(dev_name, O_RDWR | O_NONBLOCK, 0);
 if (fd < 0) {
 	perror(dev_name);