diff --git a/src/utictactoe.c b/src/utictactoe.c
index 5bf1c3b..935d1cb 100644
--- a/src/utictactoe.c
+++ b/src/utictactoe.c
@@ -102,8 +102,12 @@ int main(int argc, char* argv[]) {
             break;
 
         case 'c':
-            printf ("contest activated\n");
+            if ( OPTIONAL_ARGUMENT_IS_PRESENT ) {
+                fprintf(stderr, "Error: contest option doesn't support arguments\n");
+                exit (EXIT_FAILURE);
+            }
             contest = true;
+            printf ("contest activated\n");
             break;
         case 'V':
             printf("utictactoe %d.%d.%d\n", VERSION, SUBVERSION, REVISION);