bibtool (2.48alpha.2-4) type.c

--- bibtool-2.48alpha.2.orig/type.c
+++ bibtool-2.48alpha.2/type.c
@@ -77,7 +77,7 @@
 {						   /*                        */
   if ( s == (char *)NULL ) return;		   /*                        */
   for ( ; *s ; s++ )				   /*                        */
-  { type__allowed[*s] |= T__WordSep; }		   /*                        */
+  { type__allowed[(unsigned char)*s] |= T__WordSep; } /*                     */
 }						   /*------------------------*/
 
 #ifdef DEBUG