diff --git a/layout/mathml/base/src/nsMathMLmspaceFrame.cpp b/layout/mathml/base/src/nsMathMLmspaceFrame.cpp
index 7263a1fedd27..7671e22b32cc 100644
--- a/layout/mathml/base/src/nsMathMLmspaceFrame.cpp
+++ b/layout/mathml/base/src/nsMathMLmspaceFrame.cpp
@@ -114,7 +114,7 @@ nsMathMLmspaceFrame::Init(nsIPresContext*  aPresContext,
   if (NS_CONTENT_ATTR_HAS_VALUE == GetAttribute(mContent, mPresentationData.mstyle,
                    nsMathMLAtoms::depth_, value)) {
     if (ParseNumericValue(value, cssValue) && cssValue.IsLengthUnit()) {
-      mHeight = CalcLength(aPresContext, mStyleContext, cssValue);
+      mDepth = CalcLength(aPresContext, mStyleContext, cssValue);
     }
   }