--- a/media/libcubeb/src/cubeb_wasapi.cpp
+++ b/media/libcubeb/src/cubeb_wasapi.cpp
@@ -643,17 +643,17 @@ bool get_input_buffer(cubeb_stream * stm
     if (FAILED(hr)) {
       LOG("FAILED to release intput buffer");
       return false;
     }
     offset += packet_size * input_channel_count;
   }
 
   assert(stm->linear_input_buffer.length() >= total_available_input &&
-         offset == total_available_input);
+         offset == total_available_input * input_channel_count);
 
   return true;
 }
 
 /* Get an output buffer from the render_client. It has to be released before
  * exiting the callback. */
 bool get_output_buffer(cubeb_stream * stm, size_t max_frames, float *& buffer, size_t & frame_count)
 {