diff --git a/util/lexdimacs.mll b/util/lexdimacs.mll
index 9cc1507a..d2f544b2 100644
--- a/util/lexdimacs.mll
+++ b/util/lexdimacs.mll
@@ -8,9 +8,9 @@ let number = ['0' - '9']+
 
 rule token = parse
   | ' '                     { token lexbuf }
-  | 'c' [^ '\n']* '\n'      { token lexbuf }
   | 'p'                     { P }
   | "cnf"                   { CNF }
   | '\n'                    { EOL }
+  | "c " [^ '\n']* '\n'      { token lexbuf }
   | ['-']? number           { LIT (int_of_string (Lexing.lexeme lexbuf)) }
   | eof                     { EOF }