diff --git a/layout/base/nsPresContext.cpp b/layout/base/nsPresContext.cpp
index dc792adf8f01..b8303175748c 100644
--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -2040,12 +2040,6 @@ nsPresContext::UpdateIsChrome()
 nsPresContext::HasAuthorSpecifiedRules(const nsIFrame *aFrame,
                                        uint32_t ruleTypeMask) const
 {
-#ifdef MOZ_STYLO
-  if (!mShell || mShell->StyleSet()->IsServo()) {
-    NS_ERROR("stylo: nsPresContext::HasAuthorSpecifiedRules not implemented");
-    return true;
-  }
-#endif
   return
     nsRuleNode::HasAuthorSpecifiedRules(aFrame->StyleContext(),
                                         ruleTypeMask,
diff --git a/layout/style/nsRuleNode.cpp b/layout/style/nsRuleNode.cpp
index 5f3409e6817c..5bc1c9c2f002 100644
--- a/layout/style/nsRuleNode.cpp
+++ b/layout/style/nsRuleNode.cpp
@@ -10394,6 +10394,13 @@ nsRuleNode::HasAuthorSpecifiedRules(nsStyleContext* aStyleContext,
                                     uint32_t ruleTypeMask,
                                     bool aAuthorColorsAllowed)
 {
+#ifdef MOZ_STYLO
+  if (aStyleContext->StyleSource().IsServoComputedValues()) {
+    NS_WARNING("stylo: nsRuleNode::HasAuthorSpecifiedRules not implemented");
+    return true;
+  }
+#endif
+
   uint32_t inheritBits = 0;
   if (ruleTypeMask & NS_AUTHOR_SPECIFIED_BACKGROUND)
     inheritBits |= NS_STYLE_INHERIT_BIT(Background);