--- a/dom/media/webaudio/ScriptProcessorNode.cpp
+++ b/dom/media/webaudio/ScriptProcessorNode.cpp
@@ -335,17 +335,19 @@ public:
 
   virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const override
   {
     // Not owned:
     // - mSource (probably)
     // - mDestination (probably)
     size_t amount = AudioNodeEngine::SizeOfExcludingThis(aMallocSizeOf);
     amount += mSharedBuffers->SizeOfIncludingThis(aMallocSizeOf);
-    amount += mInputBuffer->SizeOfIncludingThis(aMallocSizeOf);
+    if (mInputBuffer) {
+      amount += mInputBuffer->SizeOfIncludingThis(aMallocSizeOf);
+    }
 
     return amount;
   }
 
   virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const override
   {
     return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
   }