diff --git a/gfx/thebes/src/gfxWindowsFonts.cpp b/gfx/thebes/src/gfxWindowsFonts.cpp
index 7559967bba9a..b112b23b3596 100644
--- a/gfx/thebes/src/gfxWindowsFonts.cpp
+++ b/gfx/thebes/src/gfxWindowsFonts.cpp
@@ -869,6 +869,8 @@ static const char *sCJKLangGroup[] = {
 
 #define STATIC_STRING_LENGTH 100
 
+#define UNICODE_ZWSP 0x200B
+
 /**
  * XXX We could use a bunch of nsAutoTArrays to avoid memory allocation
  * for non-huge strings.
@@ -1170,7 +1172,14 @@ public:
                 PRInt32 advance = mAdvances[k]*appUnitsPerDevUnit;
                 WORD glyph = mGlyphs[k];
                 if (missing) {
-                    aRun->SetMissingGlyph(runOffset, mString[offset]);
+                    // Special-case ZWSP so that it always "works" even if the
+                    // font doesn't have the glyph. Don't draw a hexbox and
+                    // don't give it width.
+                    if (mString[offset] == UNICODE_ZWSP) {
+                        aRun->SetCharacterGlyph(runOffset, g.IsMissing());
+                    } else {
+                        aRun->SetMissingGlyph(runOffset, mString[offset]);
+                    }
                 } else if (glyphCount == 1 && advance >= 0 &&
                     mOffsets[k].dv == 0 && mOffsets[k].du == 0 &&
                     gfxTextRun::CompressedGlyph::IsSimpleAdvance(advance) &&