diff --git a/du3/program.c b/du3/program.c
index 221fc1b..4882b3a 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -77,7 +77,7 @@ int main() {
             }
             print_stack(&mystack);
         } else {
-            printf("invalid input\n");
+            printf("bad input\n");
             return 1;
         }
     }