diff --git a/b2/lang.l b/b2/lang.l
index 280c789..abb5951 100644
--- a/b2/lang.l
+++ b/b2/lang.l
@@ -121,7 +121,7 @@ static void process_bom_line(const char *s)
  * ...% still as a single WORD.
  */
 
-ID	[-_A-Za-z0-9()+./]
+ID	[-_A-Za-z0-9()+./,]
 PAT	"\\"[^\t\n]|[^ \t\n\\]
 
 %s ID PAT