diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex
index 3cb2e5c39ba..09ef2f2b09e 100644
--- a/Doc/lib/libstdtypes.tex
+++ b/Doc/lib/libstdtypes.tex
@@ -1107,7 +1107,7 @@ Notes:
      
   \var{key} specifies a function of one argument that is used to
      extract a comparison key from each list element:
-     \samp{\var{cmp}=\function{str.lower}}
+     \samp{\var{key}=\function{str.lower}}
 
   \var{reverse} is a boolean value.  If set to \code{True}, then the
      list elements are sorted as if each comparison were reversed.