diff --git a/dom/media/MediaRecorder.cpp b/dom/media/MediaRecorder.cpp
index 7506fd4eda27..32d4ef389dcb 100644
--- a/dom/media/MediaRecorder.cpp
+++ b/dom/media/MediaRecorder.cpp
@@ -455,8 +455,7 @@ public:
   size_t
   SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
   {
-    size_t amount = mEncoder->SizeOfExcludingThis(aMallocSizeOf);
-    return amount;
+    return (mEncoder ?  mEncoder->SizeOfExcludingThis(aMallocSizeOf) : 0);
   }