--- a/layout/generic/nsFlexContainerFrame.cpp
+++ b/layout/generic/nsFlexContainerFrame.cpp
@@ -3300,19 +3300,19 @@ FlexboxAxisTracker::InitAxesFromModernPr
   const nsStylePosition* stylePos = aFlexContainer->StylePosition();
   uint32_t flexDirection = stylePos->mFlexDirection;
 
   // Inline dimension ("start-to-end"):
   // (NOTE: I'm intentionally not calling these "inlineAxis"/"blockAxis", since
   // those terms have explicit definition in the writing-modes spec, which are
   // the opposite of how I'd be using them here.)
   AxisOrientationType inlineDimension =
-    InlineDirToAxisOrientation(mWM.GetInlineDir());
+    InlineDirToAxisOrientation(aWM.GetInlineDir());
   AxisOrientationType blockDimension =
-    BlockDirToAxisOrientation(mWM.GetBlockDir());
+    BlockDirToAxisOrientation(aWM.GetBlockDir());
 
   // Determine main axis:
   switch (flexDirection) {
     case NS_STYLE_FLEX_DIRECTION_ROW:
       mMainAxis = inlineDimension;
       mIsRowOriented = true;
       mIsMainAxisReversed = false;
       break;