diff --git a/src/tests.rs b/src/tests.rs
index c947d1a227..056cac1a93 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -447,6 +447,14 @@ fn hide_twice_not_allowed() -> TestResult {
     )
 }
 
+#[test]
+fn def_twice_should_fail() -> TestResult {
+    fail_test(
+        r#"def foo [] { "foo" }; def foo [] { "bar" }"#,
+        "defined more than once",
+    )
+}
+
 #[test]
 fn from_json_1() -> TestResult {
     run_test(r#"('{"name": "Fred"}' | from json).name"#, "Fred")