diff --git a/tests/by-util/test_df.rs b/tests/by-util/test_df.rs
index 4206c4c82..13cfdcef4 100644
--- a/tests/by-util/test_df.rs
+++ b/tests/by-util/test_df.rs
@@ -28,6 +28,11 @@ fn test_df_compatible_si() {
     new_ucmd!().arg("-aH").succeeds();
 }
 
+#[test]
+fn test_df_compatible_sync() {
+    new_ucmd!().arg("--sync").succeeds();
+}
+
 #[test]
 fn test_df_arguments_override_themselves() {
     new_ucmd!().args(&["--help", "--help"]).succeeds();