diff --git a/gst/adder/gstadder.c b/gst/adder/gstadder.c
index e0e7b7694d..955717538a 100644
--- a/gst/adder/gstadder.c
+++ b/gst/adder/gstadder.c
@@ -223,6 +223,8 @@ gst_adder_sink_getcaps (GstPad * pad, GstCaps * filter)
 {
   GstAdder *adder;
   GstCaps *result, *peercaps, *current_caps, *filter_caps;
+  GstStructure *s;
+  gint i, n;
 
   adder = GST_ADDER (GST_PAD_PARENT (pad));
 
@@ -283,6 +285,22 @@ gst_adder_sink_getcaps (GstPad * pad, GstCaps * filter)
     }
   }
 
+  result = gst_caps_make_writable (result);
+
+  n = gst_caps_get_size (result);
+  for (i = 0; i < n; i++) {
+    GstStructure *sref;
+
+    s = gst_caps_get_structure (result, i);
+    sref = gst_structure_copy (s);
+    gst_structure_set (sref, "channels", GST_TYPE_INT_RANGE, 0, 2, NULL);
+    if (gst_structure_is_subset (s, sref)) {
+      /* This field is irrelevant when in mono or stereo */
+      gst_structure_remove_field (s, "channel-mask");
+    }
+    gst_structure_free (sref);
+  }
+
   if (filter_caps)
     gst_caps_unref (filter_caps);
 
@@ -322,9 +340,19 @@ gst_adder_sink_query (GstCollectPads * pads, GstCollectData * pad,
  * the other sinkpads because we can only mix streams with the same caps.
  */
 static gboolean
-gst_adder_setcaps (GstAdder * adder, GstPad * pad, GstCaps * caps)
+gst_adder_setcaps (GstAdder * adder, GstPad * pad, GstCaps * orig_caps)
 {
+  GstCaps *caps;
   GstAudioInfo info;
+  GstStructure *s;
+  gint channels;
+
+  caps = gst_caps_copy (orig_caps);
+
+  s = gst_caps_get_structure (caps, 0);
+  if (gst_structure_get_int (s, "channels", &channels))
+    if (channels <= 2)
+      gst_structure_remove_field (s, "channel-mask");
 
   if (!gst_audio_info_from_caps (&info, caps))
     goto invalid_format;
@@ -337,12 +365,14 @@ gst_adder_setcaps (GstAdder * adder, GstPad * pad, GstCaps * caps)
   if (adder->current_caps != NULL) {
     if (gst_audio_info_is_equal (&info, &adder->info)) {
       GST_OBJECT_UNLOCK (adder);
+      gst_caps_unref (caps);
       return TRUE;
     } else {
       GST_DEBUG_OBJECT (pad, "got input caps %" GST_PTR_FORMAT ", but "
           "current caps are %" GST_PTR_FORMAT, caps, adder->current_caps);
       GST_OBJECT_UNLOCK (adder);
       gst_pad_push_event (pad, gst_event_new_reconfigure ());
+      gst_caps_unref (caps);
       return FALSE;
     }
   }
@@ -356,11 +386,14 @@ gst_adder_setcaps (GstAdder * adder, GstPad * pad, GstCaps * caps)
 
   GST_INFO_OBJECT (pad, "handle caps change to %" GST_PTR_FORMAT, caps);
 
+  gst_caps_unref (caps);
+
   return TRUE;
 
   /* ERRORS */
 invalid_format:
   {
+    gst_caps_unref (caps);
     GST_WARNING_OBJECT (adder, "invalid format set as caps");
     return FALSE;
   }