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}]
+
 <
 
  vim:tw=78:ts=8:noet:ft=help:norl:
diff --git a/src/diff.c b/src/diff.c
index a4f3f7e..d2089dc 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -3511,9 +3511,9 @@
 	}
     }
 
-    *diff_ctxlen = dict_get_number_def(d, "context", 1);
+    *diff_ctxlen = dict_get_number_def(d, "context", 0);
     if (*diff_ctxlen < 0)
-	*diff_ctxlen = 1;
+	*diff_ctxlen = 0;
 
     if (dict_get_bool(d, "iblank", FALSE))
 	*diffopts |= DIFF_IBLANK;
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 67a1427..d13eb1c 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -1952,7 +1952,7 @@
     {"did_filetype",	0, 0, 0,	    NULL,
 			ret_number_bool,    f_did_filetype},
     {"diff",		2, 3, FEARG_1,	    arg3_diff,
-			ret_list_dict_any,  f_diff},
+			ret_any,  f_diff},
     {"diff_filler",	1, 1, FEARG_1,	    arg1_lnum,
 			ret_number,	    f_diff_filler},
     {"diff_hlID",	2, 2, FEARG_1,	    arg2_lnum_number,
diff --git a/src/testdir/dumps/Test_difffunc_diffexpr_1.dump b/src/testdir/dumps/Test_difffunc_diffexpr_1.dump
new file mode 100644
index 0000000..b103cc8
--- /dev/null
+++ b/src/testdir/dumps/Test_difffunc_diffexpr_1.dump
@@ -0,0 +1,12 @@
+| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@34||+1#0000000#ffffff0| +0#0000e05#a8a8a8255@1|z+0#0000000#5fd7ff255|e|r|o| @30
+| +0#0000e05#a8a8a8255@1>o+0#0000000#ffffff0|n|e| @31||+1&&| +0#0000e05#a8a8a8255@1|o+0#0000000#ffffff0|n|e| @31
+| +0#0000e05#a8a8a8255@1|t+0#0000000#ffd7ff255|w|o|x+2&#ff404010| +0&#ffd7ff255@30||+1&#ffffff0| +0#0000e05#a8a8a8255@1|t+0#0000000#ffd7ff255|w|o| @31
+| +0#0000e05#a8a8a8255@1|t+0#0000000#ffffff0|h|r|e@1| @29||+1&&| +0#0000e05#a8a8a8255@1|t+0#0000000#ffffff0|h|r|e@1| @29
+| +0#0000e05#a8a8a8255@1|f+0#0000000#5fd7ff255|o|u|r| @30||+1&#ffffff0| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@34
+|~+0&#ffffff0| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|~| @35||+1#0000000&|~+0#4040ff13&| @35
+|X+3#0000000&|d|i|f@2|u|n|c|2|.|t|x|t| @4|1|,|1| @11|A|l@1| |X+1&&|d|i|f@2|u|n|c|1|.|t|x|t| @4|1|,|1| @11|A|l@1
+|"+0&&|X|d|i|f@2|u|n|c|2|.|t|x|t|"| |4|L|,| |2|0|B| @50
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index d37a9a2..8e7d5ce 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
Binary files differ
diff --git a/src/version.c b/src/version.c
index 7fd6982..7a9172a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    99,
+/**/
     98,
 /**/
     97,