diff --git a/README.md b/README.md
index 1463b7d..13033d4 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ older versions might be available on a dedicated branch.
 * [hiding_type_variables.thy](hiding_type_variables.thy) provides
   print a setup for defining default type variables of type
   constructors. The default type variables can be hidden in output,
-  e.g., `('a, 'b, 'c) foo` is shown as `_ foo`. This shorthand
+  e.g., `('a, 'b, 'c) foo` is shown as `__ foo`. This shorthand
   notation can also be used in input (using a parse translation),
   which (sometimes) helps to focus on the important parts of complex
   type declarations.