diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 0dca467..0b3d59e 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -1,4 +1,4 @@
-*builtin.txt*	For Vim version 9.1.  Last change: 2024 Feb 11
+*builtin.txt*	For Vim version 9.1.  Last change: 2024 Feb 12
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2078,8 +2078,7 @@
 					use.  Supported boolean items are
 					"myers", "minimal", "patience" and
 					"histogram".
-		    context		unified diff context length.  Default
-					is 1.
+		    context		diff context length.  Default is 0.
 		    iblank		ignore changes where lines are all
 					blank.
 		    icase		ignore changes in case of text.
@@ -2092,6 +2091,10 @@
 					line.
 		For more information about these options, refer to 'diffopt'.
 
+		To compute the unified diff, all the items in {fromlist} are
+		concatenated into a string using a newline separator and the
+		same for {tolist}.  The unified diff output uses line numbers.
+
 		Returns an empty List or String if {fromlist} and {tolist} are
 		identical.
 
diff --git a/runtime/doc/diff.txt b/runtime/doc/diff.txt
index 05dd4a6..e3abbde 100644
--- a/runtime/doc/diff.txt
+++ b/runtime/doc/diff.txt
@@ -510,9 +510,14 @@
    [{'from_idx': 1, 'from_count': 2, 'to_idx': 1, 'to_count': 0}]
 
   " disjointed changes
-  :echo diff(['ab', 'def', 'ghi', 'jkl'], ['abc', 'def', 'ghi', 'jk'], {'output': 'indices'})
+  :echo diff(['ab', 'def', 'ghi', 'jkl'], ['abc', 'def', 'ghi', 'jk'], {'output': 'indices', 'context': 0})
    [{'from_idx': 0, 'from_count': 1, 'to_idx': 0, 'to_count': 1},
     {'from_idx': 3, 'from_count': 1, 'to_idx': 3, 'to_count': 1}]
+
+  " disjointed changes with context length 1
+  :echo diff(['ab', 'def', 'ghi', 'jkl'], ['abc', 'def', 'ghi', 'jk'], {'output': 'indices', 'context': 1})
+   [{'from_idx': 0, 'from_count': 4, 'to_idx': 0, 'to_count': 4}]
+
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  vim:tw=78:ts=8:noet:ft=help:norl: