diff --git a/src/translator.pl b/src/translator.pl
index 4e1985f9..90ae5a30 100644
--- a/src/translator.pl
+++ b/src/translator.pl
@@ -73,8 +73,8 @@
 %Special stream operation rewrite rules before main translation
 rewrite_streamops(['trace!', Arg1, Arg2],
                   [progn, ['println!', Arg1], Arg2]).
-rewrite_streamops([unique, [superpose|Args]],
-                  [call, [superpose, ['unique-atom', [collapse, [superpose|Args]]]]]).
+rewrite_streamops([unique, Arg],
+                  [call, [superpose, ['unique-atom', [collapse, Arg]]]]).
 rewrite_streamops([union, [superpose|A], [superpose|B]],
                   [call, [superpose, ['union-atom', [collapse, [superpose|A]],
                                                     [collapse, [superpose|B]]]]]).