diff --git a/docs/users_guide/glasgow_exts.rst b/docs/users_guide/glasgow_exts.rst
index 961a3785d029af80e70ae7723d71f41b5ac98af7..51f84d68cd82e05b99a60326939bd329190bc0b1 100644
--- a/docs/users_guide/glasgow_exts.rst
+++ b/docs/users_guide/glasgow_exts.rst
@@ -8401,6 +8401,7 @@ the printed stack is not particularly enlightening, so we might choose
 to surpress it by freezing the ``CallStack`` that we pass to ``myerror``.
 
 ::
+
    head :: (?callStack :: CallStack) => [a] -> a
    head []     = let ?callStack = freezeCallStack ?callStack in myerror "empty"
    head (x:xs) = x