--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -10999,22 +10999,33 @@ nsIPresShell::HandleGlobalZoom()
 }
 
 void
 nsIPresShell::SetGlobalZoom(const float& aZoomFactor)
 {
   MOZ_ASSERT(mPresContext, "our pres context should not be null");
   PRES_LOG("%p: SetGlobalZoom: %f\n", this, aZoomFactor);
 
+  nsCOMPtr<nsIDocShell> docShell = mPresContext->GetDocShell();
+  if (!docShell) {
+    return;
+  }
+
+  nsCOMPtr<nsIContentViewer> cv;
+  docShell->GetContentViewer(getter_AddRefs(cv));
+  if (!cv) {
+    return;
+  }
+
   if (nsLayoutUtils::BrowserGlobalZoomFull()) {
-    mPresContext->SetFullZoom(aZoomFactor);
-    mPresContext->SetTextZoom(1.0f);
+    cv->SetFullZoom(aZoomFactor);
+    cv->SetTextZoom(1.0f);
   } else {
-    mPresContext->SetFullZoom(1.0f);
-    mPresContext->SetTextZoom(aZoomFactor);
+    cv->SetFullZoom(1.0f);
+    cv->SetTextZoom(aZoomFactor);
   }
 }
 
 void
 PresShell::PausePainting()
 {
   if (GetPresContext()->RefreshDriver()->GetPresContext() != GetPresContext())
     return;