diff --git a/modules/preprocs/yapp/yapp-token.l b/modules/preprocs/yapp/yapp-token.l
index 9521126e..90997901 100644
--- a/modules/preprocs/yapp/yapp-token.l
+++ b/modules/preprocs/yapp/yapp-token.l
@@ -283,7 +283,7 @@ DIR	 %[ \t]*
 
 \n	{ line_number++; return '\n'; }
 
-[-+*/,()] { return yytext[0]; }
+[][+*/,()-] { return yytext[0]; }
 
 .	{
     Warning(_("ignoring unrecognized character `%s'"),
diff --git a/src/preprocs/yapp/yapp-token.l b/src/preprocs/yapp/yapp-token.l
index 9521126e..90997901 100644
--- a/src/preprocs/yapp/yapp-token.l
+++ b/src/preprocs/yapp/yapp-token.l
@@ -283,7 +283,7 @@ DIR	 %[ \t]*
 
 \n	{ line_number++; return '\n'; }
 
-[-+*/,()] { return yytext[0]; }
+[][+*/,()-] { return yytext[0]; }
 
 .	{
     Warning(_("ignoring unrecognized character `%s'"),