--- a/dom/ipc/TabContext.cpp
+++ b/dom/ipc/TabContext.cpp
@@ -297,18 +297,18 @@ MaybeInvalidTabContext::MaybeInvalidTabC
 {
   bool isMozBrowserElement = false;
   bool isPrerendered = false;
   uint32_t containingAppId = NO_APP_ID;
   DocShellOriginAttributes originAttributes;
   nsAutoCString originSuffix;
   nsAutoCString signedPkgOriginNoSuffix;
   nsAutoString presentationURL;
-  UIStateChangeType showAccelerators;
-  UIStateChangeType showFocusRings;
+  UIStateChangeType showAccelerators = UIStateChangeType_NoChange;
+  UIStateChangeType showFocusRings = UIStateChangeType_NoChange;
 
   switch(aParams.type()) {
     case IPCTabContext::TPopupIPCTabContext: {
       const PopupIPCTabContext &ipcContext = aParams.get_PopupIPCTabContext();
 
       TabContext *context;
       if (ipcContext.opener().type() == PBrowserOrId::TPBrowserParent) {
         context = TabParent::GetFrom(ipcContext.opener().get_PBrowserParent());