--- a/dom/activities/src/Activity.cpp
+++ b/dom/activities/src/Activity.cpp
@@ -4,22 +4,26 @@
 
 #include "Activity.h"
 #include "nsDOMClassInfo.h"
 #include "nsContentUtils.h"
 #include "nsIDOMActivityOptions.h"
 
 using namespace mozilla::dom;
 
+#ifdef MOZ_SYS_MSG
 DOMCI_DATA(MozActivity, Activity)
+#endif
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(Activity)
   NS_INTERFACE_MAP_ENTRY(nsIDOMMozActivity)
   NS_INTERFACE_MAP_ENTRY(nsIJSNativeInitializer)
+#ifdef MOZ_SYS_MSG
   NS_DOM_INTERFACE_MAP_ENTRY_CLASSINFO(MozActivity)
+#endif
 NS_INTERFACE_MAP_END_INHERITING(DOMRequest)
 
 NS_IMPL_ADDREF_INHERITED(Activity, DOMRequest)
 NS_IMPL_RELEASE_INHERITED(Activity, DOMRequest)
 
 NS_IMPL_CYCLE_COLLECTION_CLASS(Activity)
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(Activity,

--- a/dom/base/nsDOMClassInfo.cpp
+++ b/dom/base/nsDOMClassInfo.cpp
@@ -518,17 +518,19 @@ using mozilla::dom::indexedDB::IDBWrappe
 #include "BluetoothManager.h"
 #include "BluetoothAdapter.h"
 #include "BluetoothDevice.h"
 #include "BluetoothPropertyEvent.h"
 #endif
 
 #include "nsIDOMNavigatorSystemMessages.h"
 
+#ifdef MOZ_SYS_MSG
 #include "mozilla/dom/Activity.h"
+#endif
 #include "TimeManager.h"
 
 #include "DOMCameraManager.h"
 #include "DOMCameraControl.h"
 #include "DOMCameraCapabilities.h"
 
 #include "DOMError.h"
 #include "DOMRequest.h"
@@ -1686,18 +1688,20 @@ static nsDOMClassInfoData sClassInfoData
                            DOM_DEFAULT_SCRIPTABLE_FLAGS)
 
   NS_DEFINE_CLASSINFO_DATA_WITH_NAME(DOMFileHandle, FileHandle, nsEventTargetSH,
                            EVENTTARGET_SCRIPTABLE_FLAGS)
   NS_DEFINE_CLASSINFO_DATA(FileRequest, nsEventTargetSH,
                            EVENTTARGET_SCRIPTABLE_FLAGS)
   NS_DEFINE_CLASSINFO_DATA(LockedFile, nsEventTargetSH,
                            EVENTTARGET_SCRIPTABLE_FLAGS)
+#ifdef MOZ_SYS_MSG
   NS_DEFINE_CLASSINFO_DATA(MozActivity, nsEventTargetSH,
                            EVENTTARGET_SCRIPTABLE_FLAGS)
+#endif
 
   NS_DEFINE_CLASSINFO_DATA(MozTimeManager, nsDOMGenericSH,
                            DOM_DEFAULT_SCRIPTABLE_FLAGS)
 
 #ifdef MOZ_WEBRTC
   NS_DEFINE_CLASSINFO_DATA(DataChannel, nsEventTargetSH,
                            EVENTTARGET_SCRIPTABLE_FLAGS)
 #endif
@@ -1725,17 +1729,19 @@ NS_DEFINE_CONTRACT_CTOR(FileReader, NS_F
 NS_DEFINE_CONTRACT_CTOR(ArchiveReader, NS_ARCHIVEREADER_CONTRACTID)
 NS_DEFINE_CONTRACT_CTOR(FormData, NS_FORMDATA_CONTRACTID)
 NS_DEFINE_CONTRACT_CTOR(XMLSerializer, NS_XMLSERIALIZER_CONTRACTID)
 NS_DEFINE_CONTRACT_CTOR(XPathEvaluator, NS_XPATH_EVALUATOR_CONTRACTID)
 NS_DEFINE_CONTRACT_CTOR(XSLTProcessor,
                         "@mozilla.org/document-transformer;1?type=xslt")
 NS_DEFINE_CONTRACT_CTOR(EventSource, NS_EVENTSOURCE_CONTRACTID)
 NS_DEFINE_CONTRACT_CTOR(MutationObserver, NS_DOMMUTATIONOBSERVER_CONTRACTID)
+#ifdef MOZ_SYS_MSG
 NS_DEFINE_CONTRACT_CTOR(MozActivity, NS_DOMACTIVITY_CONTRACTID)
+#endif
 
 #undef NS_DEFINE_CONTRACT_CTOR
 
 #define NS_DEFINE_EVENT_CTOR(_class)                        \
   nsresult                                                  \
   NS_DOM##_class##Ctor(nsISupports** aInstancePtrResult)    \
   {                                                         \
     nsIDOMEvent* e = nullptr;                                \
@@ -1796,17 +1802,19 @@ static const nsConstructorFuncMapData kC
   NS_DEFINE_CONSTRUCTOR_FUNC_DATA(FileReader, FileReaderCtor)
   NS_DEFINE_CONSTRUCTOR_FUNC_DATA(ArchiveReader, ArchiveReaderCtor)
   NS_DEFINE_CONSTRUCTOR_FUNC_DATA(FormData, FormDataCtor)
   NS_DEFINE_CONSTRUCTOR_FUNC_DATA(XMLSerializer, XMLSerializerCtor)
   NS_DEFINE_CONSTRUCTOR_FUNC_DATA(XPathEvaluator, XPathEvaluatorCtor)
   NS_DEFINE_CONSTRUCTOR_FUNC_DATA(XSLTProcessor, XSLTProcessorCtor)
   NS_DEFINE_CONSTRUCTOR_FUNC_DATA(EventSource, EventSourceCtor)
   NS_DEFINE_CONSTRUCTOR_FUNC_DATA(MutationObserver, MutationObserverCtor)
+#ifdef MOZ_SYS_MSG
   NS_DEFINE_CONSTRUCTOR_FUNC_DATA(MozActivity, MozActivityCtor)
+#endif
 };
 
 nsIXPConnect *nsDOMClassInfo::sXPConnect = nullptr;
 nsIScriptSecurityManager *nsDOMClassInfo::sSecMan = nullptr;
 bool nsDOMClassInfo::sIsInitialized = false;
 bool nsDOMClassInfo::sDisableDocumentAllSupport = false;
 bool nsDOMClassInfo::sDisableGlobalScopePollutionSupport = false;
 
@@ -4440,21 +4448,23 @@ nsDOMClassInfo::Init()
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMDOMRequest)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMEventTarget)
   DOM_CLASSINFO_MAP_END
 
   DOM_CLASSINFO_MAP_BEGIN(LockedFile, nsIDOMLockedFile)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMLockedFile)
   DOM_CLASSINFO_MAP_END
 
+#ifdef MOZ_SYS_MSG
   DOM_CLASSINFO_MAP_BEGIN(MozActivity, nsIDOMMozActivity)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMMozActivity)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMDOMRequest)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMEventTarget)
   DOM_CLASSINFO_MAP_END
+#endif
 
   DOM_CLASSINFO_MAP_BEGIN(MozTimeManager, nsIDOMMozTimeManager)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMMozTimeManager)
   DOM_CLASSINFO_MAP_END
 
 #ifdef MOZ_WEBRTC
   DOM_CLASSINFO_MAP_BEGIN(DataChannel, nsIDOMDataChannel)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMDataChannel)

--- a/dom/base/nsDOMClassInfoClasses.h
+++ b/dom/base/nsDOMClassInfoClasses.h
@@ -514,15 +514,17 @@ DOMCI_CLASS(CameraCapabilities)
 DOMCI_CLASS(DOMError)
 DOMCI_CLASS(DOMRequest)
 DOMCI_CLASS(OpenWindowEventDetail)
 
 DOMCI_CLASS(DOMFileHandle)
 DOMCI_CLASS(FileRequest)
 DOMCI_CLASS(LockedFile)
 
+#ifdef MOZ_SYS_MSG
 DOMCI_CLASS(MozActivity)
+#endif
 
 DOMCI_CLASS(MozTimeManager)
 
 #ifdef MOZ_WEBRTC
 DOMCI_CLASS(DataChannel)
 #endif