diff --git a/dlls/winegstreamer/media_source.c b/dlls/winegstreamer/media_source.c
index f07b83f413e..43beb71838a 100644
--- a/dlls/winegstreamer/media_source.c
+++ b/dlls/winegstreamer/media_source.c
@@ -879,6 +879,12 @@ static HRESULT media_stream_init_desc(struct media_stream *stream)
         IMFMediaType *base_type = mf_media_type_from_wg_format(&format);
         GUID base_subtype;
 
+        if (!base_type)
+        {
+            hr = MF_E_INVALIDMEDIATYPE;
+            goto done;
+        }
+
         IMFMediaType_GetGUID(base_type, &MF_MT_SUBTYPE, &base_subtype);
 
         stream_types[0] = base_type;
@@ -911,8 +917,8 @@ static HRESULT media_stream_init_desc(struct media_stream *stream)
             WG_AUDIO_FORMAT_F32LE,
         };
 
-        stream_types[0] = mf_media_type_from_wg_format(&format);
-        type_count = 1;
+        if ((stream_types[0] = mf_media_type_from_wg_format(&format)))
+            type_count = 1;
 
         for (i = 0; i < ARRAY_SIZE(audio_types); i++)
         {
@@ -921,7 +927,8 @@ static HRESULT media_stream_init_desc(struct media_stream *stream)
                 continue;
             new_format = format;
             new_format.u.audio.format = audio_types[i];
-            stream_types[type_count++] = mf_media_type_from_wg_format(&new_format);
+            if ((stream_types[type_count] = mf_media_type_from_wg_format(&new_format)))
+                type_count++;
         }
     }
     else