diff --git a/builtin/grep.c b/builtin/grep.c
index d00ee76f24..61b2c27490 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -101,6 +101,9 @@ static pthread_cond_t cond_write;
 /* Signalled when we are finished with everything. */
 static pthread_cond_t cond_result;
 
+/* Synchronize the start of all threads */
+static maybe_thread_barrier_t start_barrier;
+
 static int skip_first_line;
 
 static void add_work(struct grep_opt *opt, struct grep_source *gs)
@@ -198,6 +201,8 @@ static void *run(void *arg)
 	int hit = 0;
 	struct grep_opt *opt = arg;
 
+	maybe_thread_barrier_wait(&start_barrier);
+
 	while (1) {
 		struct work_item *w = get_work();
 		if (!w)
@@ -229,6 +234,7 @@ static void start_threads(struct grep_opt *opt)
 	pthread_cond_init(&cond_add, NULL);
 	pthread_cond_init(&cond_write, NULL);
 	pthread_cond_init(&cond_result, NULL);
+	maybe_thread_barrier_init(&start_barrier, NULL, num_threads + 1);
 	grep_use_locks = 1;
 	enable_obj_read_lock();
 
@@ -248,6 +254,7 @@ static void start_threads(struct grep_opt *opt)
 			die(_("grep: failed to create thread: %s"),
 			    strerror(err));
 	}
+	maybe_thread_barrier_wait(&start_barrier);
 }
 
 static int wait_all(void)
@@ -284,6 +291,7 @@ static int wait_all(void)
 	pthread_cond_destroy(&cond_add);
 	pthread_cond_destroy(&cond_write);
 	pthread_cond_destroy(&cond_result);
+	maybe_thread_barrier_destroy(&start_barrier);
 	grep_use_locks = 0;
 	disable_obj_read_lock();