diff --git a/README.md b/README.md
index c06ffe9..3478876 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,12 @@ $ # run:
 $ snack run -- <args>
 ```
 
+Run the test suite with this command:
+
+``` bash
+$ ./script/test
+```
+
 ## Usage
 
 `niv` simplifies [adding](#add) and [updating](#update) dependencies in Nix
diff --git a/README.tpl.md b/README.tpl.md
index bb7b862..de1d7e4 100644
--- a/README.tpl.md
+++ b/README.tpl.md
@@ -22,6 +22,12 @@ $ # run:
 $ snack run -- <args>
 ```
 
+Run the test suite with this command:
+
+``` bash
+$ ./script/test
+```
+
 ## Usage
 
 `niv` simplifies [adding](#add) and [updating](#update) dependencies in Nix
diff --git a/nix/packages.nix b/nix/packages.nix
index 6906e42..0439fbe 100644
--- a/nix/packages.nix
+++ b/nix/packages.nix
@@ -24,5 +24,15 @@ rec
       template
     );
   readme-test = runCommand "README-test" {}
-    "diff ${../README.md} ${readme} && echo dummy > $out";
+    ''
+      err() {
+        echo
+        echo -e "\e[31mERR\e[0m: README.md out of date"
+        echo -e "please run \e[1m./script/gen\e[0m"
+        echo
+        exit 1
+      }
+
+      diff ${../README.md} ${readme} && echo dummy > $out || err ;
+    '';
 }