diff --git a/gst/monoscope/gstmonoscope.c b/gst/monoscope/gstmonoscope.c
index e06196b1e7..fa0d541427 100644
--- a/gst/monoscope/gstmonoscope.c
+++ b/gst/monoscope/gstmonoscope.c
@@ -255,6 +255,9 @@ gst_monoscope_src_negotiate (GstMonoscope * monoscope)
   gst_structure_fixate_field_nearest_int (structure, "width", 320);
   gst_structure_fixate_field_nearest_int (structure, "height", 240);
   gst_structure_fixate_field_nearest_fraction (structure, "framerate", 25, 1);
+  gst_structure_fixate_field_nearest_fraction (structure, "pixel-aspect-ratio",
+      1, 1);
+  target = gst_caps_fixate (target);
 
   gst_monoscope_src_setcaps (monoscope, target);