--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -10206,17 +10206,17 @@ nsFrame::BoxMetrics() const
 }
 
 void
 nsIFrame::UpdateStyleOfChildAnonBox(nsIFrame* aChildFrame,
                                     ServoRestyleState& aRestyleState)
 {
   MOZ_ASSERT(aChildFrame->GetParent() == this,
              "This should only be used for children!");
-  MOZ_ASSERT((!GetContent() && IsViewportFrame()) ||
+  MOZ_ASSERT(!GetContent() || !aChildFrame->GetContent() ||
              aChildFrame->GetContent() == GetContent(),
              "What content node is it a frame for?");
   MOZ_ASSERT(!aChildFrame->GetPrevContinuation(),
              "Only first continuations should end up here");
 
   // We could force the caller to pass in the pseudo, since some callers know it
   // statically...  But this API is a bit nicer.
   nsIAtom* pseudo = aChildFrame->StyleContext()->GetPseudo();