diff --git a/testdata/parser/negative/18.txt b/testdata/parser/negative/18.txt
new file mode 100644
index 0000000000000000000000000000000000000000..ada41541886229d2f5b288bfda713d5c92eaf328
--- /dev/null
+++ b/testdata/parser/negative/18.txt
@@ -0,0 +1,3 @@
+Parse error at 18.pdl:7:11: Unindexable expression
+	y[0] = (x+y)[0];
+	         ^