diff --git a/image/ImageFactory.cpp b/image/ImageFactory.cpp
index 03816a588394..953f61d84a0f 100644
--- a/image/ImageFactory.cpp
+++ b/image/ImageFactory.cpp
@@ -103,7 +103,7 @@ static void NotifyImageLoading(nsIURI* aURI) {
 already_AddRefed<Image> ImageFactory::CreateImage(
     nsIRequest* aRequest, ProgressTracker* aProgressTracker,
     const nsCString& aMimeType, nsIURI* aURI, bool aIsMultiPart,
-    uint32_t aInnerWindowId) {
+    uint64_t aInnerWindowId) {
   // Compute the image's initialization flags.
   uint32_t imageFlags = ComputeImageFlags(aURI, aMimeType, aIsMultiPart);
 
@@ -225,7 +225,7 @@ uint32_t GetContentSize(nsIRequest* aRequest) {
 already_AddRefed<Image> ImageFactory::CreateRasterImage(
     nsIRequest* aRequest, ProgressTracker* aProgressTracker,
     const nsCString& aMimeType, nsIURI* aURI, uint32_t aImageFlags,
-    uint32_t aInnerWindowId) {
+    uint64_t aInnerWindowId) {
   MOZ_ASSERT(aProgressTracker);
 
   nsresult rv;
@@ -253,7 +253,7 @@ already_AddRefed<Image> ImageFactory::CreateRasterImage(
 already_AddRefed<Image> ImageFactory::CreateVectorImage(
     nsIRequest* aRequest, ProgressTracker* aProgressTracker,
     const nsCString& aMimeType, nsIURI* aURI, uint32_t aImageFlags,
-    uint32_t aInnerWindowId) {
+    uint64_t aInnerWindowId) {
   MOZ_ASSERT(aProgressTracker);
 
   nsresult rv;
diff --git a/image/ImageFactory.h b/image/ImageFactory.h
index 4ee2b2a029a6..1f9b67773983 100644
--- a/image/ImageFactory.h
+++ b/image/ImageFactory.h
@@ -43,7 +43,7 @@ class ImageFactory {
                                              ProgressTracker* aProgressTracker,
                                              const nsCString& aMimeType,
                                              nsIURI* aURI, bool aIsMultiPart,
-                                             uint32_t aInnerWindowId);
+                                             uint64_t aInnerWindowId);
   /**
    * Creates a new image which isn't associated with a URI or loaded through
    * the usual image loading mechanism.
@@ -71,12 +71,12 @@ class ImageFactory {
   static already_AddRefed<Image> CreateRasterImage(
       nsIRequest* aRequest, ProgressTracker* aProgressTracker,
       const nsCString& aMimeType, nsIURI* aURI, uint32_t aImageFlags,
-      uint32_t aInnerWindowId);
+      uint64_t aInnerWindowId);
 
   static already_AddRefed<Image> CreateVectorImage(
       nsIRequest* aRequest, ProgressTracker* aProgressTracker,
       const nsCString& aMimeType, nsIURI* aURI, uint32_t aImageFlags,
-      uint32_t aInnerWindowId);
+      uint64_t aInnerWindowId);
 
   // This is a static factory class, so disallow instantiation.
   virtual ~ImageFactory() = 0;