diff --git a/mozilla/gfx/public/nsIDeviceContext.h b/mozilla/gfx/public/nsIDeviceContext.h
index 48bed64a191..aa0bd7ddeba 100644
--- a/mozilla/gfx/public/nsIDeviceContext.h
+++ b/mozilla/gfx/public/nsIDeviceContext.h
@@ -482,7 +482,7 @@ public:
    * Get the unscaled ratio of app units to dev pixels; useful if something
    * needs to be converted from to unscaled pixels
    */
-  PRInt32 UnscaledAppUnitsPerDevPixel() { return mAppUnitsPerDevNotScaledPixel; }
+  PRInt32 UnscaledAppUnitsPerDevPixel() const { return mAppUnitsPerDevNotScaledPixel; }
 
 protected:
   PRInt32 mAppUnitsPerDevPixel;
diff --git a/mozilla/gfx/src/thebes/nsThebesDeviceContext.cpp b/mozilla/gfx/src/thebes/nsThebesDeviceContext.cpp
index 89c969cf3d0..9fe9ba5aa2a 100644
--- a/mozilla/gfx/src/thebes/nsThebesDeviceContext.cpp
+++ b/mozilla/gfx/src/thebes/nsThebesDeviceContext.cpp
@@ -402,7 +402,7 @@ nsThebesDeviceContext::GetSystemFont(nsSystemFontID aID, nsFont *aFont) const
     aFont->familyNameQuirks = fontStyle.familyNameQuirks;
     aFont->weight = fontStyle.weight;
     aFont->decorations = NS_FONT_DECORATION_NONE;
-    aFont->size = NSFloatPixelsToAppUnits(fontStyle.size, AppUnitsPerDevPixel());
+    aFont->size = NSFloatPixelsToAppUnits(fontStyle.size, UnscaledAppUnitsPerDevPixel());
     //aFont->langGroup = fontStyle.langGroup;
     aFont->sizeAdjust = fontStyle.sizeAdjust;