--- a/dom/animation/EffectCompositor.cpp
+++ b/dom/animation/EffectCompositor.cpp
@@ -120,16 +120,23 @@ FindAnimationsForCompositor(const nsIFra
   MOZ_ASSERT(!aMatches || aMatches->IsEmpty(),
              "Matches array, if provided, should be empty");
 
   EffectSet* effects = EffectSet::GetEffectSet(aFrame);
   if (!effects || effects->IsEmpty()) {
     return false;
   }
 
+  // FIXME: Bug 1334036: stylo: Implement off-main-thread animations.
+  if (aFrame->StyleContext()->StyleSource().IsServoComputedValues()) {
+    NS_WARNING("stylo: return false in FindAnimationsForCompositor because "
+               "haven't supported compositor-driven animations yet");
+    return false;
+  }
+
   // First check for newly-started transform animations that should be
   // synchronized with geometric animations. We need to do this before any
   // other early returns (the one above is ok) since we can only check this
   // state when the animation is newly-started.
   if (aProperty == eCSSProperty_transform) {
     PendingAnimationTracker* tracker =
       aFrame->PresContext()->Document()->GetPendingAnimationTracker();
     if (tracker) {
@@ -144,21 +151,16 @@ FindAnimationsForCompositor(const nsIFra
       effects->PropertiesForAnimationsLevel().HasProperty(aProperty)) {
     return false;
   }
 
   if (aFrame->RefusedAsyncAnimation()) {
     return false;
   }
 
-  if (aFrame->StyleContext()->StyleSource().IsServoComputedValues()) {
-    NS_ERROR("stylo: cannot handle compositor-driven animations yet");
-    return false;
-  }
-
   // The animation cascade will almost always be up-to-date by this point
   // but there are some cases such as when we are restoring the refresh driver
   // from test control after seeking where it might not be the case.
   //
   // Those cases are probably not important but just to be safe, let's make
   // sure the cascade is up to date since if it *is* up to date, this is
   // basically a no-op.
   Maybe<NonOwningAnimationTarget> pseudoElement =
@@ -268,24 +270,24 @@ EffectCompositor::RequestRestyle(dom::El
     bool hasPendingRestyle = elementsToRestyle.Get(key);
     if (!hasPendingRestyle) {
       PostRestyleForAnimation(aElement, aPseudoType, aCascadeLevel);
     }
     elementsToRestyle.Put(key, true);
   }
 
   if (aRestyleType == RestyleType::Layer) {
-    // FIXME: we call RequestRestyle for both stylo and gecko, so we
-    // should fix this after supporting animations on the compositor.
-    // Prompt layers to re-sync their animations.
+    // FIXME: Bug 1334036: we call RequestRestyle for both stylo and gecko,
+    // so we should fix this after supporting animations on the compositor.
     if (mPresContext->RestyleManager()->IsServo()) {
-      NS_ERROR("stylo: Servo-backed style system should not be using "
-               "EffectCompositor");
+      NS_WARNING("stylo: RequestRestyle to layer, but Servo-backed style "
+                 "system haven't supported compositor-driven animations yet");
       return;
     }
+    // Prompt layers to re-sync their animations.
     mPresContext->RestyleManager()->AsGecko()->IncrementAnimationGeneration();
     EffectSet* effectSet =
       EffectSet::GetEffectSet(aElement, aPseudoType);
     if (effectSet) {
       effectSet->UpdateAnimationGeneration(mPresContext);
     }
   }
 }