diff --git a/content/base/src/nsDocument.cpp b/content/base/src/nsDocument.cpp
index 8e34b3f1990..eabfa594166 100644
--- a/content/base/src/nsDocument.cpp
+++ b/content/base/src/nsDocument.cpp
@@ -8492,10 +8492,13 @@ DispatchFullScreenChange(nsIDocument* aTarget)
 NS_IMETHODIMP
 nsDocument::MozCancelFullScreen()
 {
-  if (!nsContentUtils::IsRequestFullScreenAllowed()) {
-    return NS_OK;
+  // Only perform fullscreen changes if we're running in a webapp
+  // same-origin to the web app, or if we're in a user generated event
+  // handler.
+  if (NodePrincipal()->GetAppStatus() >= nsIPrincipal::APP_STATUS_INSTALLED ||
+      nsContentUtils::IsRequestFullScreenAllowed()) {
+    RestorePreviousFullScreenState();
   }
-  RestorePreviousFullScreenState();
   return NS_OK;
 }