--- a/content/smil/nsSMILAnimationController.cpp
+++ b/content/smil/nsSMILAnimationController.cpp
@@ -435,21 +435,28 @@ nsSMILAnimationController::AddAnimationT
   nsISMILAnimationElement* aElement, nsSMILCompositorTable* aCompositorTable)
 {
   // Add a compositor to the hash table if there's not already one there
   nsSMILCompositorKey key;
   if (!GetCompositorKeyForAnimation(aElement, key))
     // Something's wrong/missing about animation's target; skip this animation
     return;
 
-  nsSMILCompositor* result = aCompositorTable->PutEntry(key);
+  nsSMILAnimationFunction& func = aElement->AnimationFunction();
 
-  // Add this animationElement's animation function to the compositor's list of
-  // animation functions.
-  result->AddAnimationFunction(&aElement->AnimationFunction());
+  // Only add active animation functions. If there are no active animations
+  // targetting an attribute, no compositor will be created and any previously
+  // applied animations will be cleared.
+  if (func.IsActiveOrFrozen()) {
+    nsSMILCompositor* result = aCompositorTable->PutEntry(key);
+
+    // Add this animationElement's animation function to the compositor's list
+    // of animation functions.
+    result->AddAnimationFunction(&func);
+  }
 }
 
 // Helper function that, given a nsISMILAnimationElement, looks up its target
 // element & target attribute and returns a newly-constructed nsSMILCompositor
 // for this target.
 /*static*/ PRBool
 nsSMILAnimationController::GetCompositorKeyForAnimation(
     nsISMILAnimationElement* aAnimElem, nsSMILCompositorKey& aResult)

--- a/content/smil/nsSMILAnimationFunction.cpp
+++ b/content/smil/nsSMILAnimationFunction.cpp
@@ -231,17 +231,17 @@ nsSMILAnimationFunction::Inactivate(PRBo
 
 void
 nsSMILAnimationFunction::ComposeResult(const nsISMILAttr& aSMILAttr,
                                        nsSMILValue& aResult)
 {
   mHasChanged = PR_FALSE;
 
   // Skip animations that are inactive or in error
-  if (!IsActive() || mErrorFlags != 0)
+  if (!IsActiveOrFrozen() || mErrorFlags != 0)
     return;
 
   // Get the animation values
   nsSMILValueArray values;
   nsresult rv = GetValues(aSMILAttr, values);
   if (NS_FAILED(rv))
     return;
 
@@ -304,20 +304,20 @@ nsSMILAnimationFunction::ComposeResult(c
 PRInt8
 nsSMILAnimationFunction::CompareTo(const nsSMILAnimationFunction* aOther) const
 {
   NS_ENSURE_TRUE(aOther, 0);
 
   NS_ASSERTION(aOther != this, "Trying to compare to self.");
 
   // Inactive animations sort first
-  if (!IsActive() && aOther->IsActive())
+  if (!IsActiveOrFrozen() && aOther->IsActiveOrFrozen())
     return -1;
 
-  if (IsActive() && !aOther->IsActive())
+  if (IsActiveOrFrozen() && !aOther->IsActiveOrFrozen())
     return 1;
 
   // Sort based on begin time
   if (mBeginTime != aOther->GetBeginTime())
     return mBeginTime > aOther->GetBeginTime() ? 1 : -1;
 
   // XXX When syncbase timing is implemented, we next need to sort based on
   // dependencies

--- a/content/smil/nsSMILAnimationFunction.h
+++ b/content/smil/nsSMILAnimationFunction.h
@@ -171,22 +171,22 @@ public:
 
   /*
    * The following methods are provided so that the compositor can optimize its
    * operations by only composing those animation that will affect the final
    * result.
    */
 
   /**
-   * Indicates if the animation is currently active. Inactive animations will
-   * not contribute to the composed result.
+   * Indicates if the animation is currently active or frozen. Inactive
+   * animations will not contribute to the composed result.
    *
-   * @return  True if the animation active, false otherwise.
+   * @return  True if the animation is active or frozen, false otherwise.
    */
-  PRBool IsActive() const
+  PRBool IsActiveOrFrozen() const
   {
     /*
      * - Frozen animations should be considered active for the purposes of
      * compositing.
      * - This function does not assume that our nsSMILValues (by/from/to/values)
      * have already been parsed.
      */
     return (mIsActive || mIsFrozen);