diff --git a/dom/media/fmp4/MP4Reader.cpp b/dom/media/fmp4/MP4Reader.cpp
index 7e8d2b44d165..795e262cd796 100644
--- a/dom/media/fmp4/MP4Reader.cpp
+++ b/dom/media/fmp4/MP4Reader.cpp
@@ -749,18 +749,6 @@ MP4Reader::Update(TrackType aTrack)
       mFoundSPSForTelemetry = AccumulateSPSTelemetry(extradata);
     }
 
-    if (sample && sample->mMp4Sample && sample->mMp4Sample->crypto.valid) {
-      CryptoSample& crypto = sample->mMp4Sample->crypto;
-      MOZ_ASSERT(crypto.session_ids.IsEmpty());
-
-      ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
-
-      nsRefPtr<CDMProxy> proxy = mDecoder->GetCDMProxy();
-      MOZ_ASSERT(proxy);
-
-      proxy->GetSessionIdsForKeyId(crypto.key, crypto.session_ids);
-    }
-
     if (sample) {
       decoder.mDecoder->Input(sample->mMp4Sample.forget());
       if (aTrack == kVideo) {
diff --git a/dom/media/fmp4/eme/EMEDecoderModule.cpp b/dom/media/fmp4/eme/EMEDecoderModule.cpp
index a7a2f5d24281..9e8a254d619b 100644
--- a/dom/media/fmp4/eme/EMEDecoderModule.cpp
+++ b/dom/media/fmp4/eme/EMEDecoderModule.cpp
@@ -89,6 +89,9 @@ public:
       return NS_OK;
     }
 
+    mProxy->GetSessionIdsForKeyId(aSample->crypto.key,
+                                  aSample->crypto.session_ids);
+
     mProxy->Decrypt(aSample, new DeliverDecrypted(this, mTaskQueue));
     return NS_OK;
   }
@@ -162,6 +165,7 @@ public:
   EMEMediaDataDecoderProxy(nsIThread* aProxyThread, MediaDataDecoderCallback* aCallback, CDMProxy* aProxy, FlushableMediaTaskQueue* aTaskQueue)
    : MediaDataDecoderProxy(aProxyThread, aCallback)
    , mSamplesWaitingForKey(new SamplesWaitingForKey(this, aTaskQueue, aProxy))
+   , mProxy(aProxy)
   {
   }
 
@@ -170,6 +174,7 @@ public:
 
 private:
   nsRefPtr<SamplesWaitingForKey> mSamplesWaitingForKey;
+  nsRefPtr<CDMProxy> mProxy;
 };
 
 nsresult
@@ -179,6 +184,9 @@ EMEMediaDataDecoderProxy::Input(mp4_demuxer::MP4Sample* aSample)
     return NS_OK;
   }
 
+  mProxy->GetSessionIdsForKeyId(aSample->crypto.key,
+                                aSample->crypto.session_ids);
+
   return MediaDataDecoderProxy::Input(aSample);
 }
 
@@ -189,6 +197,7 @@ EMEMediaDataDecoderProxy::Shutdown()
 
   mSamplesWaitingForKey->BreakCycles();
   mSamplesWaitingForKey = nullptr;
+  mProxy = nullptr;
 
   return rv;
 }