diff --git a/src/test/run-pass/deref-lval.rs b/src/test/run-pass/deref-lval.rs
index ff76f9e61923..cd17329b2f39 100644
--- a/src/test/run-pass/deref-lval.rs
+++ b/src/test/run-pass/deref-lval.rs
@@ -1,4 +1,4 @@
-fn main() {
+impure fn main() {
     auto x = @mutable 5;
     *x = 1000;
     log *x;