diff --git a/builtin/grep.c b/builtin/grep.c
index 40b9a93127482bebf6dc8c9eb39b2104711a543a..f427d55f274889a7fcfbd12e3c21678ad947f32e 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -96,6 +96,9 @@ static pthread_cond_t cond_write;
 /* Signalled when we are finished with everything. */
 static pthread_cond_t cond_result;
 
+static int print_hunk_marks_between_files;
+static int printed_something;
+
 static void add_work(enum work_type type, char *name, void *id)
 {
 	grep_lock();
@@ -159,7 +162,12 @@ static void work_done(struct work_item *w)
 	for(; todo[todo_done].done && todo_done != todo_start;
 	    todo_done = (todo_done+1) % ARRAY_SIZE(todo)) {
 		w = &todo[todo_done];
-		write_or_die(1, w->out.buf, w->out.len);
+		if (w->out.len) {
+			if (print_hunk_marks_between_files && printed_something)
+				write_or_die(1, "--\n", 3);
+			write_or_die(1, w->out.buf, w->out.len);
+			printed_something = 1;
+		}
 		free(w->name);
 		free(w->identifier);
 	}
@@ -926,8 +934,11 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	if (online_cpus() == 1 || !grep_threads_ok(&opt))
 		use_threads = 0;
 
-	if (use_threads)
+	if (use_threads) {
+		if (opt.pre_context || opt.post_context)
+			print_hunk_marks_between_files = 1;
 		start_threads(&opt);
+	}
 #else
 	use_threads = 0;
 #endif
diff --git a/grep.c b/grep.c
index 90a063a985098976f831c37227496d612fae37c0..e5f06e435f2a8100676cd2a5b78312fcd8631717 100644
--- a/grep.c
+++ b/grep.c
@@ -551,8 +551,6 @@ static void show_line(struct grep_opt *opt, char *bol, char *eol,
 		if (opt->last_shown == 0) {
 			if (opt->show_hunk_mark)
 				opt->output(opt, "--\n", 3);
-			else
-				opt->show_hunk_mark = 1;
 		} else if (lno > opt->last_shown + 1)
 			opt->output(opt, "--\n", 3);
 	}
@@ -750,14 +748,6 @@ int grep_threads_ok(const struct grep_opt *opt)
 	    !opt->name_only)
 		return 0;
 
-	/* If we are showing hunk marks, we should not do it for the
-	 * first match. The synchronization problem we get for this
-	 * constraint is not yet solved, so we disable threading in
-	 * this case.
-	 */
-	if (opt->pre_context || opt->post_context)
-		return 0;
-
 	return 1;
 }
 
@@ -779,11 +769,14 @@ static int grep_buffer_1(struct grep_opt *opt, const char *name,
 	enum grep_context ctx = GREP_CONTEXT_HEAD;
 	xdemitconf_t xecfg;
 
-	opt->last_shown = 0;
-
 	if (!opt->output)
 		opt->output = std_output;
 
+	if (opt->last_shown && (opt->pre_context || opt->post_context) &&
+	    opt->output == std_output)
+		opt->show_hunk_mark = 1;
+	opt->last_shown = 0;
+
 	if (buffer_is_binary(buf, size)) {
 		switch (opt->binary) {
 		case GREP_BINARY_DEFAULT: