--- a/dom/base/nsFrameLoader.cpp
+++ b/dom/base/nsFrameLoader.cpp
@@ -1343,16 +1343,25 @@ nsFrameLoader::SwapWithOtherRemoteLoader
   if (!ourShell || !otherShell) {
     return NS_ERROR_NOT_IMPLEMENTED;
   }
 
   if (!mRemoteBrowser || !aOther->mRemoteBrowser) {
     return NS_ERROR_NOT_IMPLEMENTED;
   }
 
+  // Remote types must match to swap loaders.
+  const nsAString& currentRemoteType =
+    mRemoteBrowser->Manager()->AsContentParent()->GetRemoteType();
+  const nsAString& newRemoteType =
+    aOther->mRemoteBrowser->Manager()->AsContentParent()->GetRemoteType();
+  if (!currentRemoteType.Equals(newRemoteType)) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+
   if (mRemoteBrowser->IsIsolatedMozBrowserElement() !=
       aOther->mRemoteBrowser->IsIsolatedMozBrowserElement()) {
     return NS_ERROR_NOT_IMPLEMENTED;
   }
 
   // When we swap docShells, maybe we have to deal with a new page created just
   // for this operation. In this case, the browser code should already have set
   // the correct userContextId attribute value in the owning XULElement, but our

--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -1089,16 +1089,22 @@ ContentParent::GetAllEvenIfDead(nsTArray
 {
   aArray.Clear();
 
   for (auto* cp : AllProcesses(eAll)) {
     aArray.AppendElement(cp);
   }
 }
 
+const nsAString&
+ContentParent::GetRemoteType() const
+{
+  return mRemoteType;
+}
+
 void
 ContentParent::Init()
 {
   nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
   if (obs) {
     size_t length = ArrayLength(sObserverTopics);
     for (size_t i = 0; i < length; ++i) {
       obs->AddObserver(this, sObserverTopics[i], false);

--- a/dom/ipc/ContentParent.h
+++ b/dom/ipc/ContentParent.h
@@ -157,16 +157,18 @@ public:
                 Element* aFrameElement,
                 ContentParent* aOpenerContentParent,
                 bool aFreshProcess = false);
 
   static void GetAll(nsTArray<ContentParent*>& aArray);
 
   static void GetAllEvenIfDead(nsTArray<ContentParent*>& aArray);
 
+  const nsAString& GetRemoteType() const;
+
   enum CPIteratorPolicy {
     eLive,
     eAll
   };
 
   class ContentParentIterator {
   private:
     ContentParent* mCurrent;