diff --git a/testdata/parser/negative/6.pdl b/testdata/parser/negative/6.pdl
new file mode 100644
index 0000000000000000000000000000000000000000..7f523a40d6a8bf1b7912888956be1a8da25803c6
--- /dev/null
+++ b/testdata/parser/negative/6.pdl
@@ -0,0 +1,8 @@
+#version 100
+
+import std.reo;
+
+// duplicate formal parameters
+composite main(in a, out a) {
+	new sync(a, a);
+}