diff --git a/readme.md b/readme.md
index 9222ea9..25e1149 100644
--- a/readme.md
+++ b/readme.md
@@ -139,7 +139,7 @@ To test with multiple shells in sequence, use something like:
     done
 
 #### (c) Cross shell tests with `urchin -x` (experimental)
-If you run urchin with the `-sh` flag, it will be as if you ran
+If you run urchin with the `-x` flag, it will be as if you ran
 `$TEST_SHELL`. Unless `$TEST_SHELL` isn't set, in which case it'll
 be as if you ran `/bin/sh`. Putting this in she shebang line might
 eventually work out to be a cleaner way of doing cross-shell testing.
@@ -147,6 +147,11 @@ eventually work out to be a cleaner way of doing cross-shell testing.
     #!/usr/bin/env urchin -x
     test a = a
 
+It might make sense if you do this.
+
+    export TEST_SHELL=zsh && urchin -x
+    export TEST_SHELL=bash && urchin -x
+
 ## Alternatives to Urchin
 Alternatives to Urchin are discussed in
 [this blog post](https://blog.scraperwiki.com/2012/12/how-to-test-shell-scripts/).