--- a/layout/style/nsTransitionManager.cpp
+++ b/layout/style/nsTransitionManager.cpp
@@ -1005,20 +1005,16 @@ nsTransitionManager::ConsiderInitiatingT
     new ElementPropertyTransition(aTarget.mElement->OwnerDoc(), target, timing,
                                   startForReversingTest, reversePortion,
                                   effectOptions);
 
   pt->SetKeyframes(GetTransitionKeyframes(aProperty,
                                           Move(startValue), Move(endValue), tf),
                    aNewStyle);
 
-  MOZ_ASSERT(mPresContext->RestyleManager()->IsGecko(),
-             "ServoRestyleManager should not use nsTransitionManager "
-             "for transitions");
-
   RefPtr<CSSTransition> animation =
     new CSSTransition(mPresContext->Document()->GetScopeObject());
   animation->SetOwningElement(
     OwningElementRef(*aTarget.mElement, aTarget.mPseudoType));
   animation->SetTimelineNoUpdate(timeline);
   animation->SetCreationSequence(
     mPresContext->RestyleManager()->GetAnimationGeneration());
   animation->SetEffectFromStyle(pt);