--- a/dom/file/nsHostObjectURI.cpp
+++ b/dom/file/nsHostObjectURI.cpp
@@ -58,16 +58,23 @@ nsHostObjectURI::GetPrincipalUri(nsIURI*
   return NS_OK;
 }
 
 // nsISerializable methods:
 
 NS_IMETHODIMP
 nsHostObjectURI::Read(nsIObjectInputStream* aStream)
 {
+  NS_NOTREACHED("Use nsIURIMutator.read() instead");
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+nsresult
+nsHostObjectURI::ReadPrivate(nsIObjectInputStream *aStream)
+{
   nsresult rv = mozilla::net::nsSimpleURI::ReadPrivate(aStream);
   NS_ENSURE_SUCCESS(rv, rv);
 
   nsCOMPtr<nsISupports> supports;
   rv = NS_ReadOptionalObject(aStream, true, getter_AddRefs(supports));
   NS_ENSURE_SUCCESS(rv, rv);
 
   mPrincipal = do_QueryInterface(supports, &rv);

--- a/dom/file/nsHostObjectURI.h
+++ b/dom/file/nsHostObjectURI.h
@@ -66,16 +66,17 @@ public:
 
   nsCOMPtr<nsIPrincipal> mPrincipal;
 
 protected:
   virtual ~nsHostObjectURI() {}
 
   nsresult SetScheme(const nsACString &aProtocol) override;
   bool Deserialize(const mozilla::ipc::URIParams&);
+  nsresult ReadPrivate(nsIObjectInputStream *stream);
 
 public:
   class Mutator final
     : public nsIURIMutator
     , public BaseURIMutator<nsHostObjectURI>
     , public nsIPrincipalURIMutator
     , public nsISerializable
   {