diff --git a/tests/issues.rs b/tests/issues.rs
new file mode 100644
index 00000000..2eaff818
--- /dev/null
+++ b/tests/issues.rs
@@ -0,0 +1,50 @@
+mod support;
+
+use tokio::io::{AsyncBufRead, AsyncWrite};
+
+use lsp_types::{
+    DocumentSymbolParams, DocumentSymbolResponse, PublishDiagnosticsParams, TextDocumentIdentifier,
+};
+
+async fn document_symbols(
+    stdin: &mut (dyn AsyncWrite + std::marker::Unpin + Send),
+    stdout: &mut (dyn AsyncBufRead + std::marker::Unpin + Send),
+    id: u64,
+    uri: &str,
+) -> DocumentSymbolResponse {
+    support::run_method_call::<lsp_types::lsp_request!("textDocument/documentSymbol")>(
+        stdin,
+        stdout,
+        id,
+        DocumentSymbolParams {
+            text_document: TextDocumentIdentifier {
+                uri: support::test_url(uri),
+            },
+            work_done_progress_params: Default::default(),
+            partial_result_params: Default::default(),
+        },
+    )
+    .await
+    .unwrap()
+}
+
+#[test]
+fn issue_40() {
+    support::send_rpc(|stdin, stdout| {
+        Box::pin(async move {
+            let text = r#"
+type U = (Int, Int)
+
+()
+"#;
+            support::did_open(stdin, "test.glu", text).await;
+
+            let diagnostic: PublishDiagnosticsParams =
+                support::expect_notification(&mut *stdout).await;
+
+            assert_eq!(diagnostic.uri, support::test_url("test.glu"));
+
+            document_symbols(stdin, stdout, 1, "test.glu").await;
+        })
+    });
+}
diff --git a/tests/support/mod.rs b/tests/support/mod.rs
index 0cb69b30..8882e5d4 100644
--- a/tests/support/mod.rs
+++ b/tests/support/mod.rs
@@ -55,6 +55,22 @@ where
         .await
 }
 
+pub async fn run_method_call<T>(
+    writer: &mut (dyn AsyncWrite + std::marker::Unpin + Send),
+    reader: &mut (dyn AsyncBufRead + std::marker::Unpin + Send),
+    id: u64,
+    value: T::Params,
+) -> T::Result
+where
+    T: lsp_types::request::Request,
+{
+    let call = method_call(T::METHOD, id, value);
+
+    write_message(writer, call).await.unwrap();
+
+    expect_response(reader).await
+}
+
 pub fn method_call<T>(method: &str, id: u64, value: T) -> Call
 where
     T: Serialize,