diff --git a/builtin-grep.c b/builtin-grep.c
index 73fc922c49..48998af911 100644
--- a/builtin-grep.c
+++ b/builtin-grep.c
@@ -278,6 +278,17 @@ static int flush_grep(struct grep_opt *opt,
 		argc -= 2;
 	}
 
+	if (opt->pre_context || opt->post_context) {
+		/*
+		 * grep handles hunk marks between files, but we need to
+		 * do that ourselves between multiple calls.
+		 */
+		if (opt->show_hunk_mark)
+			write_or_die(1, "--\n", 3);
+		else
+			opt->show_hunk_mark = 1;
+	}
+
 	status = exec_grep(argc, argv);
 
 	if (kept_0) {
diff --git a/grep.c b/grep.c
index 6ee80f7fd9..4bca759b67 100644
--- a/grep.c
+++ b/grep.c
@@ -491,7 +491,12 @@ static void show_line(struct grep_opt *opt, char *bol, char *eol,
 	int rest = eol - bol;
 
 	if (opt->pre_context || opt->post_context) {
-		if (opt->last_shown && lno > opt->last_shown + 1)
+		if (opt->last_shown == 0) {
+			if (opt->show_hunk_mark)
+				fputs("--\n", stdout);
+			else
+				opt->show_hunk_mark = 1;
+		} else if (lno > opt->last_shown + 1)
 			fputs("--\n", stdout);
 	}
 	opt->last_shown = lno;
diff --git a/grep.h b/grep.h
index 0883214a09..730ffd6f53 100644
--- a/grep.h
+++ b/grep.h
@@ -85,6 +85,7 @@ struct grep_opt {
 	unsigned pre_context;
 	unsigned post_context;
 	unsigned last_shown;
+	int show_hunk_mark;
 };
 
 extern void append_grep_pattern(struct grep_opt *opt, const char *pat, const char *origin, int no, enum grep_pat_token t);
diff --git a/t/t7002-grep.sh b/t/t7002-grep.sh
index 7868af8f18..155bfdb7d7 100755
--- a/t/t7002-grep.sh
+++ b/t/t7002-grep.sh
@@ -155,6 +155,28 @@ test_expect_success 'grep -e A --and --not -e B' '
 	test_cmp expected actual
 '
 
+cat >expected <<EOF
+y:y yy
+--
+z:zzz
+EOF
+
+# Create 1024 file names that sort between "y" and "z" to make sure
+# the two files are handled by different calls to an external grep.
+# This depends on MAXARGS in builtin-grep.c being 1024 or less.
+c32="0 1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n o p q r s t u v"
+test_expect_success 'grep -C1, hunk mark between files' '
+	for a in $c32; do for b in $c32; do : >y-$a$b; done; done &&
+	git add y-?? &&
+	git grep -C1 "^[yz]" >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'grep -C1 --no-ext-grep, hunk mark between files' '
+	git grep -C1 --no-ext-grep "^[yz]" >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'log grep setup' '
 	echo a >>file &&
 	test_tick &&