diff --git a/runtime/doc/diff.txt b/runtime/doc/diff.txt
index 452d0ac..8c1f03a 100644
--- a/runtime/doc/diff.txt
+++ b/runtime/doc/diff.txt
@@ -1,4 +1,4 @@
-*diff.txt*      For Vim version 8.1.  Last change: 2019 Jun 02
+*diff.txt*      For Vim version 8.1.  Last change: 2019 Jul 27
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -335,7 +335,7 @@
 FINDING THE DIFFERENCES					*diff-diffexpr*
 
 The 'diffexpr' option can be set to use something else than the standard
-"diff" program to compare two files and find the differences.
+"diff" program to compare two files and find the differences. *E959*
 
 When 'diffexpr' is empty, Vim uses this command to find the differences
 between file1 and file2: >