diff --git a/du4/program.c b/du4/program.c
index e4f75fb..5cb3c45 100644
--- a/du4/program.c
+++ b/du4/program.c
@@ -73,7 +73,7 @@ int main() {
             if (fabs(result - expected) < 0.001) {
                 printf("OK\n");
             } else {
-                printf("OK\n");
+                printf("ZLE\n");
             }
         }