diff --git a/libtransmission/metainfo.c b/libtransmission/metainfo.c
index 25d91c3ed..801a4a774 100644
--- a/libtransmission/metainfo.c
+++ b/libtransmission/metainfo.c
@@ -29,7 +29,7 @@
 /***********************************************************************
  * Local prototypes
  **********************************************************************/
-#define strcatUTF8( dst, src) _strcatUTF8( (dst), sizeof( dst ), (src) )
+#define strcatUTF8( dst, src) _strcatUTF8( (dst), sizeof( dst ) - 1, (src) )
 static void _strcatUTF8( char *, int, char * );
 
 /***********************************************************************