--- a/media/webrtc/signaling/src/jsep/JsepSessionImpl.cpp
+++ b/media/webrtc/signaling/src/jsep/JsepSessionImpl.cpp
@@ -2047,16 +2047,23 @@ JsepSessionImpl::ValidateAnswer(const Sd
         offerAttrs.HasAttribute(SdpAttribute::kMidAttribute) &&
         offerAttrs.GetMid() != answerAttrs.GetMid()) {
       JSEP_SET_ERROR("Answer changes mid for level, was \'"
                      << offerMsection.GetAttributeList().GetMid()
                      << "\', now \'"
                      << answerMsection.GetAttributeList().GetMid() << "\'");
       return NS_ERROR_INVALID_ARG;
     }
+
+    if (answerAttrs.HasAttribute(SdpAttribute::kSetupAttribute, true) &&
+        answerAttrs.GetSetup().mRole == SdpSetupAttribute::kActpass) {
+      JSEP_SET_ERROR("Answer contains illegal setup attribute \"actpass\""
+                     " at level " << i);
+      return NS_ERROR_INVALID_ARG;
+    }
   }
 
   return NS_OK;
 }
 
 nsresult
 JsepSessionImpl::CreateReceivingTrack(size_t mline,
                                       const Sdp& sdp,