diff --git a/gfx/thebes/gfxDWriteFontList.cpp b/gfx/thebes/gfxDWriteFontList.cpp
index 88d7af7f0041..851faf6d9430 100644
--- a/gfx/thebes/gfxDWriteFontList.cpp
+++ b/gfx/thebes/gfxDWriteFontList.cpp
@@ -50,6 +50,8 @@
 
 #include "nsIWindowsRegKey.h"
 
+using namespace mozilla;
+
 #ifdef PR_LOGGING
 
 #define LOG_FONTLIST(args) PR_LOG(gfxPlatform::GetLog(eGfxLog_fontlist), \
@@ -433,6 +435,41 @@ gfxDWriteFontEntry::InitLogFont(IDWriteFont *aFont, LOGFONTW *aLogFont)
     return (FAILED(hr) ? PR_FALSE : PR_TRUE);
 }
 
+PRBool
+gfxDWriteFontEntry::IsCJKFont()
+{
+    if (mIsCJK != UNINITIALIZED_VALUE) {
+        return mIsCJK;
+    }
+
+    mIsCJK = PR_FALSE;
+
+    const PRUint32 kOS2Tag = TRUETYPE_TAG('O','S','/','2');
+    AutoFallibleTArray<PRUint8,128> buffer;
+    if (GetFontTable(kOS2Tag, buffer) != NS_OK) {
+        return mIsCJK;
+    }
+
+    // ulCodePageRange bit definitions for the CJK codepages,
+    // from http://www.microsoft.com/typography/otspec/os2.htm#cpr
+    const PRUint32 CJK_CODEPAGE_BITS =
+        (1 << 17) | // codepage 932 - JIS/Japan
+        (1 << 18) | // codepage 936 - Chinese (simplified)
+        (1 << 19) | // codepage 949 - Korean Wansung
+        (1 << 20) | // codepage 950 - Chinese (traditional)
+        (1 << 21);  // codepage 1361 - Korean Johab
+
+    if (buffer.Length() >= offsetof(OS2Table, sxHeight)) {
+        const OS2Table* os2 =
+            reinterpret_cast<const OS2Table*>(buffer.Elements());
+        if ((PRUint32(os2->codePageRange1) & CJK_CODEPAGE_BITS) != 0) {
+            mIsCJK = PR_TRUE;
+        }
+    }
+
+    return mIsCJK;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // gfxDWriteFontList
 
diff --git a/gfx/thebes/gfxDWriteFontList.h b/gfx/thebes/gfxDWriteFontList.h
index f07d7d29d99f..ad2ae5362c84 100644
--- a/gfx/thebes/gfxDWriteFontList.h
+++ b/gfx/thebes/gfxDWriteFontList.h
@@ -103,8 +103,9 @@ public:
 
         weight = NS_MAX<PRUint16>(100, weight);
         weight = NS_MIN<PRUint16>(900, weight);
-
         mWeight = weight;
+
+        mIsCJK = UNINITIALIZED_VALUE;
     }
 
     /**
@@ -130,6 +131,7 @@ public:
         mItalic = aItalic;
         mIsUserFont = PR_TRUE;
         mIsLocalUserFont = PR_TRUE;
+        mIsCJK = UNINITIALIZED_VALUE;
     }
 
     /**
@@ -152,6 +154,7 @@ public:
         mStretch = aStretch;
         mItalic = aItalic;
         mIsUserFont = PR_TRUE;
+        mIsCJK = UNINITIALIZED_VALUE;
     }
 
     virtual ~gfxDWriteFontEntry();
@@ -162,6 +165,9 @@ public:
                                   FallibleTArray<PRUint8>& aBuffer);
 
     nsresult ReadCMAP();
+
+    PRBool IsCJKFont();
+
 protected:
     friend class gfxDWriteFont;
     friend class gfxDWriteFontList;
@@ -182,6 +188,8 @@ protected:
     nsRefPtr<IDWriteFont> mFont;
     nsRefPtr<IDWriteFontFile> mFontFile;
     DWRITE_FONT_FACE_TYPE mFaceType;
+
+    PRBool mIsCJK;
 };
 
 
diff --git a/gfx/thebes/gfxDWriteFonts.cpp b/gfx/thebes/gfxDWriteFonts.cpp
index daac42153d6a..ba0ade37c7c1 100644
--- a/gfx/thebes/gfxDWriteFonts.cpp
+++ b/gfx/thebes/gfxDWriteFonts.cpp
@@ -225,7 +225,9 @@ gfxDWriteFont::ComputeMetrics()
         mAdjustedSize = mStyle.size;
     }
 
-    if (HasBitmapStrikeForSize(NS_lround(mAdjustedSize))) {
+    gfxDWriteFontEntry *fe =
+        static_cast<gfxDWriteFontEntry*>(mFontEntry.get());
+    if (fe->IsCJKFont() && HasBitmapStrikeForSize(NS_lround(mAdjustedSize))) {
         mAdjustedSize = NS_lround(mAdjustedSize);
         mUseSubpixelPositions = PR_FALSE;
         // if we have bitmaps, we need to tell Cairo NOT to use subpixel AA,