diff --git a/gst/videotestsrc/gstvideotestsrc.c b/gst/videotestsrc/gstvideotestsrc.c
index 3c762b0fef..6b0847b3db 100644
--- a/gst/videotestsrc/gstvideotestsrc.c
+++ b/gst/videotestsrc/gstvideotestsrc.c
@@ -320,9 +320,14 @@ gst_video_test_src_src_fixate (GstBaseSrc * bsrc, GstCaps * caps)
   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", 30, 1);
+
   if (gst_structure_has_field (structure, "pixel-aspect-ratio"))
     gst_structure_fixate_field_nearest_fraction (structure,
         "pixel-aspect-ratio", 1, 1);
+  else
+    gst_structure_set (structure, "pixel-aspect-ratio", GST_TYPE_FRACTION, 1, 1,
+        NULL);
+
   if (gst_structure_has_field (structure, "colorimetry"))
     gst_structure_fixate_field_string (structure, "colorimetry", "bt601");
   if (gst_structure_has_field (structure, "chroma-site"))
@@ -331,6 +336,9 @@ gst_video_test_src_src_fixate (GstBaseSrc * bsrc, GstCaps * caps)
   if (gst_structure_has_field (structure, "interlace-mode"))
     gst_structure_fixate_field_string (structure, "interlace-mode",
         "progressive");
+  else
+    gst_structure_set (structure, "interlace-mode", G_TYPE_STRING,
+        "progressive", NULL);
 
   caps = GST_BASE_SRC_CLASS (parent_class)->fixate (bsrc, caps);