diff --git a/src/cminus.l b/src/cminus.l
index 7785a61..486c61d 100644
--- a/src/cminus.l
+++ b/src/cminus.l
@@ -55,7 +55,7 @@ whitespace  [ \t]+
 "/*"             { char now, prev;
                   do
                   { now = input();
-                    if (now == EOF) break;
+                    if (now == 0) break;
                     else if (now == '\n') lineno++;
                     else if (now == '/' && prev == '*') break;
                     prev = now;