--- a/layout/style/ServoBindings.cpp
+++ b/layout/style/ServoBindings.cpp
@@ -430,22 +430,21 @@ Gecko_StyleAnimationsEquals(RawGeckoStyl
                             RawGeckoStyleAnimationListBorrowed aB)
 {
   return *aA == *aB;
 }
 
 void
 Gecko_UpdateAnimations(RawGeckoElementBorrowed aElement,
                        nsIAtom* aPseudoTagOrNull,
-                       ServoComputedValuesBorrowed aComputedValues,
+                       ServoComputedValuesBorrowedOrNull aComputedValues,
                        ServoComputedValuesBorrowedOrNull aParentComputedValues)
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(aElement);
-  MOZ_ASSERT(aComputedValues);
 
   nsPresContext* presContext = nsContentUtils::GetContextForContent(aElement);
   if (!presContext) {
     return;
   }
 
   if (presContext->IsDynamic() && aElement->IsInComposedDoc()) {
     presContext->AnimationManager()->

--- a/layout/style/ServoBindings.h
+++ b/layout/style/ServoBindings.h
@@ -190,17 +190,17 @@ Gecko_GetHTMLPresentationAttrDeclaration
 RawServoDeclarationBlockStrong
 Gecko_GetAnimationRule(RawGeckoElementBorrowed aElement,
                        nsIAtom* aPseudoTag,
                        mozilla::EffectCompositor::CascadeLevel aCascadeLevel);
 bool Gecko_StyleAnimationsEquals(RawGeckoStyleAnimationListBorrowed,
                                  RawGeckoStyleAnimationListBorrowed);
 void Gecko_UpdateAnimations(RawGeckoElementBorrowed aElement,
                             nsIAtom* aPseudoTagOrNull,
-                            ServoComputedValuesBorrowed aComputedValues,
+                            ServoComputedValuesBorrowedOrNull aComputedValues,
                             ServoComputedValuesBorrowedOrNull aParentComputedValues);
 bool Gecko_ElementHasCSSAnimations(RawGeckoElementBorrowed aElement,
                                    nsIAtom* aPseudoTagOrNull);
 
 // Atoms.
 nsIAtom* Gecko_Atomize(const char* aString, uint32_t aLength);
 void Gecko_AddRefAtom(nsIAtom* aAtom);
 void Gecko_ReleaseAtom(nsIAtom* aAtom);

--- a/layout/style/nsAnimationManager.cpp
+++ b/layout/style/nsAnimationManager.cpp
@@ -1059,22 +1059,27 @@ nsAnimationManager::UpdateAnimations(
              "Should not update animations for print or print preview");
   MOZ_ASSERT(aElement->IsInComposedDoc(),
              "Should not update animations that are not attached to the "
              "document tree");
 
   CSSPseudoElementType pseudoType =
     nsCSSPseudoElements::GetPseudoType(aPseudoTagOrNull,
                                        CSSEnabledState::eForAllContent);
+  if (!aComputedValues) {
+    // If we are in a display:none subtree we will have no computed values.
+    // Since CSS animations should not run in display:none subtrees we should
+    // stop (actually, destroy) any animations on this element here.
+    StopAnimationsForElement(aElement, pseudoType);
+    return;
+  }
+
   NonOwningAnimationTarget target(aElement, pseudoType);
   ServoCSSAnimationBuilder builder(aComputedValues, aParentComputedValues);
 
-  // Currently we don't seem to call this UpdateAnimations for elements in
-  // display:none subtree. We will call this function for such elements with
-  // null computed values in bug 1341985.
   const nsStyleDisplay *disp = Servo_GetStyleDisplay(aComputedValues);
   DoUpdateAnimations(target, *disp, builder);
 }
 
 template<class BuilderType>
 void
 nsAnimationManager::DoUpdateAnimations(
   const NonOwningAnimationTarget& aTarget,