--- a/layout/style/nsStyleAnimation.cpp
+++ b/layout/style/nsStyleAnimation.cpp
@@ -558,17 +558,17 @@ nsStyleAnimation::ComputeDistance(nsCSSP
       nsCSSUnit unit[3];
       unit[0] = GetCommonUnit(aProperty, triplet1->mXValue.GetUnit(),
                               triplet2->mXValue.GetUnit());
       unit[1] = GetCommonUnit(aProperty, triplet1->mYValue.GetUnit(),
                               triplet2->mYValue.GetUnit());
       unit[2] = GetCommonUnit(aProperty, triplet1->mZValue.GetUnit(),
                               triplet2->mZValue.GetUnit());
       if (unit[0] == eCSSUnit_Null || unit[1] == eCSSUnit_Null ||
-          unit[0] == eCSSUnit_URL) {
+          unit[2] == eCSSUnit_Null) {
         return false;
       }
 
       double squareDistance = 0.0;
       static nsCSSValue nsCSSValueTriplet::* const pairValues[3] = {
         &nsCSSValueTriplet::mXValue, &nsCSSValueTriplet::mYValue, &nsCSSValueTriplet::mZValue
       };
       for (PRUint32 i = 0; i < 3; ++i) {
@@ -1784,17 +1784,17 @@ nsStyleAnimation::AddWeighted(nsCSSPrope
       nsCSSUnit unit[3];
       unit[0] = GetCommonUnit(aProperty, triplet1.mXValue.GetUnit(),
                               triplet2.mXValue.GetUnit());
       unit[1] = GetCommonUnit(aProperty, triplet1.mYValue.GetUnit(),
                                triplet2.mYValue.GetUnit());
       unit[2] = GetCommonUnit(aProperty, triplet1.mZValue.GetUnit(),
                               triplet2.mZValue.GetUnit());
       if (unit[0] == eCSSUnit_Null || unit[1] == eCSSUnit_Null ||
-          unit[0] == eCSSUnit_Null || unit[0] == eCSSUnit_URL) {
+          unit[2] == eCSSUnit_Null) {
         return false;
       }
 
       nsAutoPtr<nsCSSValueTriplet> result(new nsCSSValueTriplet);
       static nsCSSValue nsCSSValueTriplet::* const tripletValues[3] = {
         &nsCSSValueTriplet::mXValue, &nsCSSValueTriplet::mYValue, &nsCSSValueTriplet::mZValue
       };
       PRUint32 restrictions = nsCSSProps::ValueRestrictions(aProperty);