diff --git a/tests/ui/invalid-input-impl-anyway.rs b/tests/ui/invalid-input-impl-anyway.rs
new file mode 100644
index 0000000..f9a10d8
--- /dev/null
+++ b/tests/ui/invalid-input-impl-anyway.rs
@@ -0,0 +1,11 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error]
+pub struct MyError;
+
+fn main() {
+    // FIXME: there should be no error on the following line. Thiserror should
+    // emit an Error impl regardless of the bad attribute.
+    _ = &MyError as &dyn std::error::Error;
+}
diff --git a/tests/ui/invalid-input-impl-anyway.stderr b/tests/ui/invalid-input-impl-anyway.stderr
new file mode 100644
index 0000000..297b100
--- /dev/null
+++ b/tests/ui/invalid-input-impl-anyway.stderr
@@ -0,0 +1,13 @@
+error: expected attribute arguments in parentheses: #[error(...)]
+ --> tests/ui/invalid-input-impl-anyway.rs:4:3
+  |
+4 | #[error]
+  |   ^^^^^
+
+error[E0277]: the trait bound `MyError: std::error::Error` is not satisfied
+  --> tests/ui/invalid-input-impl-anyway.rs:10:9
+   |
+10 |     _ = &MyError as &dyn std::error::Error;
+   |         ^^^^^^^^ the trait `std::error::Error` is not implemented for `MyError`
+   |
+   = note: required for the cast from `&MyError` to `&dyn std::error::Error`