diff --git a/gfx/thebes/gfxPlatformFontList.cpp b/gfx/thebes/gfxPlatformFontList.cpp
index 5bd72346458c..575c6a8674dd 100644
--- a/gfx/thebes/gfxPlatformFontList.cpp
+++ b/gfx/thebes/gfxPlatformFontList.cpp
@@ -1761,6 +1761,12 @@ eFontPrefLang gfxPlatformFontList::GetFontPrefLangFor(uint32_t aCh) {
     case UBLOCK_CJK_UNIFIED_IDEOGRAPHS_EXTENSION_F:
     case UBLOCK_KANA_EXTENDED_A:
       return eFontPrefLang_CJKSet;
+    case UBLOCK_MATHEMATICAL_OPERATORS:
+    case UBLOCK_MATHEMATICAL_ALPHANUMERIC_SYMBOLS:
+    case UBLOCK_MISCELLANEOUS_MATHEMATICAL_SYMBOLS_A:
+    case UBLOCK_MISCELLANEOUS_MATHEMATICAL_SYMBOLS_B:
+    case UBLOCK_SUPPLEMENTAL_MATHEMATICAL_OPERATORS:
+      return eFontPrefLang_Mathematics;
     default:
       return eFontPrefLang_Others;
   }