diff --git a/dom/media/tests/mochitest/test_peerConnection_setLocalAnswerInHaveLocalOffer.html b/dom/media/tests/mochitest/test_peerConnection_setLocalAnswerInHaveLocalOffer.html
index ab5ff099e6ef..191e664b27bb 100644
--- a/dom/media/tests/mochitest/test_peerConnection_setLocalAnswerInHaveLocalOffer.html
+++ b/dom/media/tests/mochitest/test_peerConnection_setLocalAnswerInHaveLocalOffer.html
@@ -21,7 +21,7 @@ runNetworkTest(function () {
       test.pcLocal._latest_offer.type = "answer";
       return test.pcLocal.setLocalDescriptionAndFail(test.pcLocal._latest_offer)
         .then(err => {
-          is(err.name, "InvalidStateError", "Error is InvalidStateError");
+          is(err.name, "InvalidModificationError", "Error is InvalidModificationError");
         });
     }
   ]);
diff --git a/dom/media/tests/mochitest/test_peerConnection_setLocalAnswerInStable.html b/dom/media/tests/mochitest/test_peerConnection_setLocalAnswerInStable.html
index 35e0654d18c1..a3f37ecc64fb 100644
--- a/dom/media/tests/mochitest/test_peerConnection_setLocalAnswerInStable.html
+++ b/dom/media/tests/mochitest/test_peerConnection_setLocalAnswerInStable.html
@@ -21,7 +21,7 @@ runNetworkTest(function () {
       test.pcLocal._latest_offer.type = "answer";
       return test.pcLocal.setLocalDescriptionAndFail(test.pcLocal._latest_offer)
         .then(err => {
-          is(err.name, "InvalidStateError", "Error is InvalidStateError");
+          is(err.name, "InvalidModificationError", "Error is InvalidModificationError");
         });
     }
   ]);
diff --git a/media/webrtc/signaling/gtest/jsep_session_unittest.cpp b/media/webrtc/signaling/gtest/jsep_session_unittest.cpp
index ad964222ef28..27256406786a 100644
--- a/media/webrtc/signaling/gtest/jsep_session_unittest.cpp
+++ b/media/webrtc/signaling/gtest/jsep_session_unittest.cpp
@@ -5288,7 +5288,7 @@ TEST_F(JsepSessionTest, SetLocalAnswerInHaveLocalOffer) {
   // SetLocalDescription call fails.
   JsepSession::Result result =
       mSessionOff->SetLocalDescription(kJsepSdpAnswer, offer);
-  ASSERT_EQ(dom::PCError::InvalidStateError, *result.mError);
+  ASSERT_EQ(dom::PCError::InvalidModificationError, *result.mError);
   ASSERT_EQ(kJsepStateHaveLocalOffer, mSessionOff->GetState());
 }
 
@@ -5320,7 +5320,7 @@ TEST_F(JsepSessionTest, SetLocalOfferInHaveRemoteOffer) {
   // SetLocalDescription call fails.
   JsepSession::Result result =
       mSessionAns->SetLocalDescription(kJsepSdpOffer, offer);
-  ASSERT_EQ(dom::PCError::InvalidStateError, *result.mError);
+  ASSERT_EQ(dom::PCError::InvalidModificationError, *result.mError);
   ASSERT_EQ(kJsepStateHaveRemoteOffer, mSessionAns->GetState());
 }
 
diff --git a/testing/web-platform/tests/webrtc/RTCPeerConnection-setLocalDescription-answer.html b/testing/web-platform/tests/webrtc/RTCPeerConnection-setLocalDescription-answer.html
index e8b3ef5071e4..c97021b0fabb 100644
--- a/testing/web-platform/tests/webrtc/RTCPeerConnection-setLocalDescription-answer.html
+++ b/testing/web-platform/tests/webrtc/RTCPeerConnection-setLocalDescription-answer.html
@@ -153,9 +153,9 @@
 
     return pc.createOffer()
     .then(offer =>
-      promise_rejects(t, 'InvalidStateError',
+      promise_rejects(t, 'InvalidModificationError',
         pc.setLocalDescription({ type: 'answer', sdp: offer.sdp })));
-  }, 'Calling setLocalDescription(answer) from stable state should reject with InvalidStateError');
+  }, 'Calling setLocalDescription(answer) from stable state should reject with InvalidModificationError');
 
   promise_test(t => {
     const pc = new RTCPeerConnection();
@@ -167,9 +167,9 @@
       pc.setLocalDescription(offer)
       .then(() => generateAnswer(offer)))
     .then(answer =>
-      promise_rejects(t, 'InvalidStateError',
+      promise_rejects(t, 'InvalidModificationError',
         pc.setLocalDescription(answer)));
-  }, 'Calling setLocalDescription(answer) from have-local-offer state should reject with InvalidStateError');
+  }, 'Calling setLocalDescription(answer) from have-local-offer state should reject with InvalidModificationError');
 
   promise_test(async t => {
     const pc1 = new RTCPeerConnection();