diff --git a/pep-0483.txt b/pep-0483.txt
index 97cfcaef422..35ae23d6771 100644
--- a/pep-0483.txt
+++ b/pep-0483.txt
@@ -486,7 +486,7 @@ replaced by the most-derived base class among ``t1``, etc. Examples:
   Note that the type checker will reject this function::
 
     def concat(first: U, second: U) -> U:
-        return x + y  # Error: can't concatenate str and bytes
+        return first + second  # Error: can't concatenate str and bytes
 
   For such cases where parameters could change their types only simultaneously
   one should use constrained type variables.