diff --git a/grammars/progsys/X-Word Lines.bnf b/grammars/progsys/X-Word Lines.bnf
index b60db411..66aa3575 100644
--- a/grammars/progsys/X-Word Lines.bnf	
+++ b/grammars/progsys/X-Word Lines.bnf	
@@ -9,7 +9,7 @@
 <assign> ::= <bool_var>' = '<bool>|<int_assign>|<string_var>' = '<string>
 <number> ::= <number><num>|<num>
 <num> ::= '0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9'
-<comp_op> ::= '<'|'>'|'=='|'>='|'<='|'!='|'is'|'is not'
+<comp_op> ::= '<'|'>'|'=='|'>='|'<='|'!='
 <string_const_part> ::= <string_const_part><string_literal>|<string_literal>
 <bool_var> ::= 'b0'|'b1'|'b2'
 <bool> ::= <bool_var>|<bool_const>|'not '<bool>|'( '<bool>' '<bool_op>' '<bool>' )'|<int>' '<comp_op>' '<int>|<string>' in '<string>|<string>' not in '<string>|<string>' == '<string>|<string>' != '<string>|<string>'.startswith('<string>')'|<string>'.endswith('<string>')'