diff --git a/coders/thumbnail.c b/coders/thumbnail.c
index 1f16349..7e1a06e 100644
--- a/coders/thumbnail.c
+++ b/coders/thumbnail.c
@@ -209,7 +209,7 @@
   write_info=CloneImageInfo(image_info);
   (void) SetImageInfo(write_info,1,&image->exception);
   if (LocaleCompare(write_info->magick,"THUMBNAIL") == 0)
-    (void) FormatMagickString(thumbnail_image->filename,MaxTextExtent,
+    (void) FormatLocaleString(thumbnail_image->filename,MaxTextExtent,
       "miff:%s",write_info->filename);
   status=WriteImage(write_info,thumbnail_image);
   thumbnail_image=DestroyImage(thumbnail_image);