--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -7084,23 +7084,25 @@ nsIFrame::ListGeneric(nsACString& aTo, c
   aTo += nsPrintfCString(" [sc=%p", static_cast<void*>(mStyleContext));
   if (mStyleContext) {
     nsIAtom* pseudoTag = mStyleContext->GetPseudo();
     if (pseudoTag) {
       nsAutoString atomString;
       pseudoTag->ToString(atomString);
       aTo += nsPrintfCString("%s", NS_LossyConvertUTF16toASCII(atomString).get());
     }
-    if (!mStyleContext->GetParent() ||
-        (GetParent() && GetParent()->StyleContext() != mStyleContext->GetParent())) {
-      aTo += nsPrintfCString("^%p", mStyleContext->GetParent());
-      if (mStyleContext->GetParent()) {
-        aTo += nsPrintfCString("^%p", mStyleContext->GetParent()->GetParent());
-        if (mStyleContext->GetParent()->GetParent()) {
-          aTo += nsPrintfCString("^%p", mStyleContext->GetParent()->GetParent()->GetParent());
+    if (mStyleContext->StyleSource().IsGeckoRuleNodeOrNull()) {
+      if (!mStyleContext->GetParent() ||
+          (GetParent() && GetParent()->StyleContext() != mStyleContext->GetParent())) {
+        aTo += nsPrintfCString("^%p", mStyleContext->GetParent());
+        if (mStyleContext->GetParent()) {
+          aTo += nsPrintfCString("^%p", mStyleContext->GetParent()->GetParent());
+          if (mStyleContext->GetParent()->GetParent()) {
+            aTo += nsPrintfCString("^%p", mStyleContext->GetParent()->GetParent()->GetParent());
+          }
         }
       }
     }
   }
   aTo += "]";
 }
 
 void