diff --git a/gfx/thebes/src/gfxPangoFonts.cpp b/gfx/thebes/src/gfxPangoFonts.cpp
index d4a87a1dc9a7..6f1af979e9f5 100644
--- a/gfx/thebes/src/gfxPangoFonts.cpp
+++ b/gfx/thebes/src/gfxPangoFonts.cpp
@@ -864,6 +864,7 @@ gfxPangoFontGroup::InitTextRun(gfxTextRun *aTextRun, const gchar *aUTF8Text,
     CreateGlyphRunsXft(aTextRun, aUTF8Text + aUTF8HeaderLength, aUTF8Length - aUTF8HeaderLength);
 #else
 #if defined(ENABLE_XFT_FAST_PATH_8BIT)
+    // We need to always use Pango for RTL text, in case glyph mirroring is required
     if (aTake8BitPath && !aTextRun->IsRightToLeft()) {
         CreateGlyphRunsXft(aTextRun, aUTF8Text + aUTF8HeaderLength, aUTF8Length - aUTF8HeaderLength);
         return;