--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -3939,19 +3939,19 @@ nsChangeHint nsStyleUIReset::CalcDiffere
 //
 
 nsStyleVariables::nsStyleVariables(StyleStructContext aContext)
 {
   MOZ_COUNT_CTOR(nsStyleVariables);
 }
 
 nsStyleVariables::nsStyleVariables(const nsStyleVariables& aSource)
+  : mVariables(aSource.mVariables)
 {
   MOZ_COUNT_CTOR(nsStyleVariables);
-  mVariables = aSource.mVariables;
 }
 
 nsStyleVariables::~nsStyleVariables(void)
 {
   MOZ_COUNT_DTOR(nsStyleVariables);
 }
 
 nsChangeHint