diff --git a/mozilla/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp b/mozilla/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp
index 90b2db5339e..bcbb8d12e39 100644
--- a/mozilla/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp
+++ b/mozilla/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp
@@ -1290,7 +1290,7 @@ nsWebBrowserPersist::GetExtensionForContentType(const PRUnichar *aContentType, P
     rv = mMIMEService->GetPrimaryExtension(contentType, EmptyCString(), ext);
     if (NS_SUCCEEDED(rv))
     {
-        *aExt = ToNewUnicode(ext);
+        *aExt = UTF8ToNewUnicode(ext);
         NS_ENSURE_TRUE(*aExt, NS_ERROR_OUT_OF_MEMORY);
         return NS_OK;
     }
diff --git a/mozilla/mailnews/mime/src/mimemoz2.cpp b/mozilla/mailnews/mime/src/mimemoz2.cpp
index 5e7c37cc207..85c04d01405 100644
--- a/mozilla/mailnews/mime/src/mimemoz2.cpp
+++ b/mozilla/mailnews/mime/src/mimemoz2.cpp
@@ -287,7 +287,7 @@ ValidateRealName(nsMsgAttachmentData *aAttach, MimeHeaders *aHdrs)
       if (NS_SUCCEEDED(rv) && !fileExtension.IsEmpty())
       {
         newAttachName.Append(PRUnichar('.'));
-        newAttachName.AppendWithConversion(fileExtension);
+        AppendUTF8toUTF16(fileExtension, newAttachName);
       }
     }