diff --git a/libfprint/drivers/vfs101.c b/libfprint/drivers/vfs101.c
index e7667c87..ca77901a 100644
--- a/libfprint/drivers/vfs101.c
+++ b/libfprint/drivers/vfs101.c
@@ -708,6 +708,9 @@ vfs_check_contrast (FpDeviceVfs101 *vdev)
   int y;
   long int count = 0;
 
+  if (vdev->height <= 0)
+    return;
+
   /* Check difference from byte 4 to byte 5 for verify contrast of image */
   for (y = 0; y < vdev->height; y++)
     count = count + vdev->buffer[offset (5, y)] - vdev->buffer[offset (4, y)];