--- a/ipc/glue/ProtocolUtils.cpp
+++ b/ipc/glue/ProtocolUtils.cpp
@@ -48,18 +48,19 @@ MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLAT
                                           ::LocalFree)
 MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(ScopedPSecurityDescriptor, \
                                           RemovePointer<PSECURITY_DESCRIPTOR>::Type, \
                                           ::LocalFree)
 #endif
 
 namespace ipc {
 
-IToplevelProtocol::IToplevelProtocol(ProtocolId aProtoId)
- : mProtocolId(aProtoId)
+IToplevelProtocol::IToplevelProtocol(ProtocolId aProtoId, Side aSide)
+ : IProtocol(aSide),
+   mProtocolId(aProtoId)
 {
 }
 
 IToplevelProtocol::~IToplevelProtocol()
 {
   if (mTrans) {
     RefPtr<DeleteTask<Transport>> task = new DeleteTask<Transport>(mTrans.release());
     XRE_GetIOMessageLoop()->PostTask(task.forget());

--- a/ipc/glue/ProtocolUtils.h
+++ b/ipc/glue/ProtocolUtils.h
@@ -147,17 +147,17 @@ public:
         NormalShutdown,
         AbnormalShutdown
     };
 
     typedef base::ProcessId ProcessId;
     typedef IPC::Message Message;
     typedef IPC::MessageInfo MessageInfo;
 
-    IProtocol() : mManager(nullptr), mChannel(nullptr) {}
+    IProtocol(Side aSide) : mSide(aSide), mManager(nullptr), mChannel(nullptr) {}
 
     virtual int32_t Register(IProtocol*);
     virtual int32_t RegisterID(IProtocol*, int32_t);
     virtual IProtocol* Lookup(int32_t);
     virtual void Unregister(int32_t);
     virtual void RemoveManagee(int32_t, IProtocol*) = 0;
 
     virtual Shmem::SharedMemory* CreateSharedMemory(
@@ -184,16 +184,17 @@ public:
     virtual const MessageChannel* GetIPCChannel() const { return mChannel; }
     virtual MessageChannel* GetIPCChannel() { return mChannel; }
 
 protected:
     void SetManager(IProtocol* aManager) { mManager = aManager; }
     void SetIPCChannel(MessageChannel* aChannel) { mChannel = aChannel; }
 
 private:
+    Side mSide;
     IProtocol* mManager;
     MessageChannel* mChannel;
 };
 
 typedef IPCMessageStart ProtocolId;
 
 template<class PFooSide>
 class Endpoint;
@@ -204,17 +205,17 @@ class Endpoint;
  * IToplevelProtocol tracks all top-level protocol actors created from
  * this protocol actor.
  */
 class IToplevelProtocol : public IProtocol
 {
     template<class PFooSide> friend class Endpoint;
 
 protected:
-    explicit IToplevelProtocol(ProtocolId aProtoId);
+    explicit IToplevelProtocol(ProtocolId aProtoId, Side aSide);
     ~IToplevelProtocol();
 
 public:
     void SetTransport(UniquePtr<Transport> aTrans)
     {
         mTrans = Move(aTrans);
     }
 

--- a/ipc/ipdl/ipdl/lower.py
+++ b/ipc/ipdl/ipdl/lower.py
@@ -2941,36 +2941,36 @@ class _GenerateProtocolActorCode(ipdl.as
             [ Label.PUBLIC ]
             + self.standardTypedefs()
             + [ Whitespace.NL ]
         ))
 
         self.cls.addstmt(Label.PUBLIC)
         # Actor()
         ctor = ConstructorDefn(ConstructorDecl(self.clsname))
+        side = ExprVar('mozilla::ipc::' + self.side.title() + 'Side')
         if ptype.isToplevel():
             ctor.memberinits = [
+                ExprMemberInit(ExprVar('mozilla::ipc::IToplevelProtocol'),
+                               [_protocolId(ptype), side]),
                 ExprMemberInit(p.channelVar(), [
                     ExprCall(ExprVar('ALLOW_THIS_IN_INITIALIZER_LIST'),
                              [ ExprVar.THIS ]) ]),
                 ExprMemberInit(p.lastActorIdVar(),
                                [ p.actorIdInit(self.side) ]),
                 ExprMemberInit(p.otherPidVar(),
                                [ ExprVar('mozilla::ipc::kInvalidProcessId') ]),
                 ExprMemberInit(p.lastShmemIdVar(),
                                [ p.shmemIdInit(self.side) ]),
                 ExprMemberInit(p.stateVar(),
                                [ p.startState() ])
             ]
-            if ptype.isToplevel():
-                ctor.memberinits = [ExprMemberInit(
-                    p.openedProtocolInterfaceType(),
-                    [ _protocolId(ptype) ])] + ctor.memberinits
         else:
             ctor.memberinits = [
+                ExprMemberInit(ExprVar('mozilla::ipc::IProtocol'), [side]),
                 ExprMemberInit(p.idVar(), [ ExprLiteral.ZERO ]),
                 ExprMemberInit(p.stateVar(),
                                [ p.deadState() ])
             ]
 
         ctor.addstmt(StmtExpr(ExprCall(ExprVar('MOZ_COUNT_CTOR'),
                                        [ ExprVar(self.clsname) ])))
         self.cls.addstmts([ ctor, Whitespace.NL ])