--- a/dom/animation/KeyframeEffectReadOnly.cpp
+++ b/dom/animation/KeyframeEffectReadOnly.cpp
@@ -891,17 +891,20 @@ KeyframeEffectReadOnly::BuildProperties(
   // make a copy of |mKeyframes| first and iterate over that instead.
   auto keyframesCopy(mKeyframes);
 
   nsTArray<ComputedKeyframeValues> computedValues =
     KeyframeUtils::GetComputedKeyframeValues(keyframesCopy,
                                              mTarget->mElement,
                                              aStyleContext);
 
-  if (mEffectOptions.mSpacingMode == SpacingMode::paced) {
+  // FIXME: Bug 1332633: we have to implement ComputeDistance for
+  //        RawServoAnimationValue.
+  if (mEffectOptions.mSpacingMode == SpacingMode::paced &&
+      aStyleContext->PresContext()->StyleSet()->IsGecko()) {
     KeyframeUtils::ApplySpacing(keyframesCopy, SpacingMode::paced,
                                 mEffectOptions.mPacedProperty,
                                 computedValues, aStyleContext);
   }
 
   result =
     KeyframeUtils::GetAnimationPropertiesFromKeyframes(keyframesCopy,
                                                        computedValues,