diff --git a/widget/src/xpwidgets/nsPrintOptionsImpl.cpp b/widget/src/xpwidgets/nsPrintOptionsImpl.cpp
index 7fa0077b396..02bc545468d 100644
--- a/widget/src/xpwidgets/nsPrintOptionsImpl.cpp
+++ b/widget/src/xpwidgets/nsPrintOptionsImpl.cpp
@@ -333,7 +333,7 @@ const char* nsPrintOptions::GetPrefName(const char *    aPrefName,
 
   if (aPrinterName.Length()) {
     mPrefName.Append("printer_");
-    mPrefName.AppendWithConversion(aPrinterName);
+    AppendUTF16toUTF8(aPrinterName, mPrefName);
     mPrefName.Append(".");
   }
   mPrefName += aPrefName;