--- a/dom/crypto/WebCryptoTask.cpp
+++ b/dom/crypto/WebCryptoTask.cpp
@@ -558,34 +558,34 @@ public:
 
     // Cache parameters depending on the specific algorithm
     TelemetryAlgorithm telemetryAlg;
     if (algName.EqualsLiteral(WEBCRYPTO_ALG_AES_CBC)) {
       CHECK_KEY_ALGORITHM(aKey.Algorithm(), WEBCRYPTO_ALG_AES_CBC);
 
       mMechanism = CKM_AES_CBC_PAD;
       telemetryAlg = TA_AES_CBC;
-      AesCbcParams params;
+      RootedDictionary<AesCbcParams> params(aCx);
       nsresult rv = Coerce(aCx, params, aAlgorithm);
       if (NS_FAILED(rv)) {
         mEarlyRv = NS_ERROR_DOM_INVALID_ACCESS_ERR;
         return;
       }
 
       ATTEMPT_BUFFER_INIT(mIv, params.mIv)
       if (mIv.Length() != 16) {
         mEarlyRv = NS_ERROR_DOM_DATA_ERR;
         return;
       }
     } else if (algName.EqualsLiteral(WEBCRYPTO_ALG_AES_CTR)) {
       CHECK_KEY_ALGORITHM(aKey.Algorithm(), WEBCRYPTO_ALG_AES_CTR);
 
       mMechanism = CKM_AES_CTR;
       telemetryAlg = TA_AES_CTR;
-      AesCtrParams params;
+      RootedDictionary<AesCtrParams> params(aCx);
       nsresult rv = Coerce(aCx, params, aAlgorithm);
       if (NS_FAILED(rv)) {
         mEarlyRv = NS_ERROR_DOM_SYNTAX_ERR;
         return;
       }
 
       ATTEMPT_BUFFER_INIT(mIv, params.mCounter)
       if (mIv.Length() != 16) {
@@ -594,17 +594,17 @@ public:
       }
 
       mCounterLength = params.mLength;
     } else if (algName.EqualsLiteral(WEBCRYPTO_ALG_AES_GCM)) {
       CHECK_KEY_ALGORITHM(aKey.Algorithm(), WEBCRYPTO_ALG_AES_GCM);
 
       mMechanism = CKM_AES_GCM;
       telemetryAlg = TA_AES_GCM;
-      AesGcmParams params;
+      RootedDictionary<AesGcmParams> params(aCx);
       nsresult rv = Coerce(aCx, params, aAlgorithm);
       if (NS_FAILED(rv)) {
         mEarlyRv = NS_ERROR_DOM_SYNTAX_ERR;
         return;
       }
 
       ATTEMPT_BUFFER_INIT(mIv, params.mIv)