diff --git a/layout/style/nsStyleStruct.cpp b/layout/style/nsStyleStruct.cpp
index ee49683ebfee306e23aed808006fd34f4db6d4c6..d7f55a861aa8a3d1e4d8c343b7da008ee559fd8a 100644
--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -3231,6 +3231,9 @@ nsStyleUIReset::nsStyleUIReset()
       mWindowShadow(StyleWindowShadow::Auto),
       mWindowOpacity(1.0),
       mMozWindowInputRegionMargin(StyleLength::Zero()),
+      mWindowTransformOrigin{LengthPercentage::FromPercentage(0.5),
+                                   LengthPercentage::FromPercentage(0.5),
+                                   {0.}},
       mTransitions(
           nsStyleAutoArray<StyleTransition>::WITH_SINGLE_INITIAL_ELEMENT),
       mTransitionTimingFunctionCount(1),
@@ -3275,6 +3278,7 @@ nsStyleUIReset::nsStyleUIReset(const nsStyleUIReset& aSource)
       mWindowOpacity(aSource.mWindowOpacity),
       mMozWindowInputRegionMargin(aSource.mMozWindowInputRegionMargin),
       mMozWindowTransform(aSource.mMozWindowTransform),
+      mWindowTransformOrigin(aSource.mWindowTransformOrigin),
       mTransitions(aSource.mTransitions.Clone()),
       mTransitionTimingFunctionCount(aSource.mTransitionTimingFunctionCount),
       mTransitionDurationCount(aSource.mTransitionDurationCount),