diff --git a/runtime/doc/diff.txt b/runtime/doc/diff.txt
index a66df1e..e5321c5 100644
--- a/runtime/doc/diff.txt
+++ b/runtime/doc/diff.txt
@@ -376,6 +376,9 @@
 'diffopt' option.  'diffexpr' cannot change the value of 'lines' and
 'columns'.
 
+The advantage of using a function call without arguments is that it is faster,
+see |expr-option-function|.
+
 Example (this does almost the same as 'diffexpr' being empty): >
 
 	set diffexpr=MyDiff()
@@ -441,6 +444,9 @@
 	v:fname_diff		patch file
 	v:fname_out		resulting patched file
 
+The advantage of using a function call without arguments is that it is faster,
+see |expr-option-function|.
+
 Example (this does the same as 'patchexpr' being empty): >
 
 	set patchexpr=MyPatch()