--- a/layout/style/nsTransitionManager.cpp
+++ b/layout/style/nsTransitionManager.cpp
@@ -565,17 +565,17 @@ nsTransitionManager::ConsiderStartingTra
              "Should have one animation property segment for a transition");
   if (haveCurrentTransition && haveValues &&
       oldPT->Properties()[0].mSegments[0].mToValue == endValue) {
     // GetAnimationRule already called RestyleForAnimation.
     return;
   }
 
   if (!shouldAnimate) {
-    if (haveCurrentTransition && !oldPT->IsFinishedTransition()) {
+    if (haveCurrentTransition) {
       // We're in the middle of a transition, and just got a non-transition
       // style change to something that we can't animate.  This might happen
       // because we got a non-transition style change changing to the current
       // in-progress value (which is particularly easy to cause when we're
       // currently in the 'transition-delay').  It also might happen because we
       // just got a style change to a value that can't be interpolated.
       AnimationPtrArray& animations = aElementTransitions->mAnimations;
       animations[currentIndex]->CancelFromStyle();
@@ -602,17 +602,17 @@ nsTransitionManager::ConsiderStartingTra
   }
 
   StyleAnimationValue startForReversingTest = startValue;
   double reversePortion = 1.0;
 
   // If the new transition reverses an existing one, we'll need to
   // handle the timing differently.
   if (haveCurrentTransition &&
-      !oldPT->IsFinishedTransition() &&
+      aElementTransitions->mAnimations[currentIndex]->HasCurrentEffect() &&
       oldPT->mStartForReversingTest == endValue) {
     // Compute the appropriate negative transition-delay such that right
     // now we'd end up at the current position.
     double valuePortion =
       oldPT->CurrentValuePortion() * oldPT->mReversePortion +
       (1.0 - oldPT->mReversePortion);
     // A timing function with negative y1 (or y2!) might make
     // valuePortion negative.  In this case, we still want to apply our