diff --git a/ext/opus/gstopusdec.c b/ext/opus/gstopusdec.c
index 829d029e09..a21b1878bc 100644
--- a/ext/opus/gstopusdec.c
+++ b/ext/opus/gstopusdec.c
@@ -214,14 +214,18 @@ gst_opus_dec_negotiate (GstOpusDec * dec, const GstAudioChannelPosition * pos)
   GstStructure *s;
   GstAudioInfo info;
 
-  caps = gst_caps_truncate (caps);
-
-  caps = gst_caps_make_writable (caps);
-  s = gst_caps_get_structure (caps, 0);
-  gst_structure_fixate_field_nearest_int (s, "rate", 48000);
-  gst_structure_get_int (s, "rate", &dec->sample_rate);
-  gst_structure_fixate_field_nearest_int (s, "channels", dec->n_channels);
-  gst_structure_get_int (s, "channels", &dec->n_channels);
+  if (caps) {
+    caps = gst_caps_truncate (caps);
+    caps = gst_caps_make_writable (caps);
+    s = gst_caps_get_structure (caps, 0);
+    gst_structure_fixate_field_nearest_int (s, "rate", 48000);
+    gst_structure_get_int (s, "rate", &dec->sample_rate);
+    gst_structure_fixate_field_nearest_int (s, "channels", dec->n_channels);
+    gst_structure_get_int (s, "channels", &dec->n_channels);
+    gst_caps_unref (caps);
+  } else {
+    dec->sample_rate = 48000;
+  }
 
   GST_INFO_OBJECT (dec, "Negotiated %d channels, %d Hz", dec->n_channels,
       dec->sample_rate);