diff --git a/sideband.c b/sideband.c
index 861f6219db..1b14ff8892 100644
--- a/sideband.c
+++ b/sideband.c
@@ -46,3 +46,29 @@ int recv_sideband(const char *me, int in_stream, int out, int err, char *buf, in
 	}
 	return 0;
 }
+
+/*
+ * fd is connected to the remote side; send the sideband data
+ * over multiplexed packet stream.
+ */
+ssize_t send_sideband(int fd, int band, const char *data, ssize_t sz, int packet_max)
+{
+	ssize_t ssz = sz;
+	const char *p = data;
+
+	while (sz) {
+		unsigned n;
+		char hdr[5];
+
+		n = sz;
+		if (packet_max - 5 < n)
+			n = packet_max - 5;
+		sprintf(hdr, "%04x", n + 5);
+		hdr[4] = band;
+		safe_write(fd, hdr, 5);
+		safe_write(fd, p, n);
+		p += n;
+		sz -= n;
+	}
+	return ssz;
+}
diff --git a/sideband.h b/sideband.h
index 90b385580e..c645cf2c52 100644
--- a/sideband.h
+++ b/sideband.h
@@ -7,5 +7,6 @@
 #define DEFAULT_PACKET_MAX 1000
 
 int recv_sideband(const char *me, int in_stream, int out, int err, char *, int);
+ssize_t send_sideband(int fd, int band, const char *data, ssize_t sz, int packet_max);
 
 #endif
diff --git a/upload-pack.c b/upload-pack.c
index 51ce936b06..1f2f7f75e5 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -4,6 +4,7 @@
 #include "cache.h"
 #include "refs.h"
 #include "pkt-line.h"
+#include "sideband.h"
 #include "tag.h"
 #include "object.h"
 #include "commit.h"
@@ -33,45 +34,19 @@ static int strip(char *line, int len)
 	return len;
 }
 
-#define PACKET_MAX 1000
 static ssize_t send_client_data(int fd, const char *data, ssize_t sz)
 {
-	ssize_t ssz;
-	const char *p;
-
-	if (!data) {
-		if (!use_sideband)
-			return 0;
-		packet_flush(1);
-	}
-
-	if (!use_sideband) {
-		if (fd == 3)
-			/* emergency quit */
-			fd = 2;
-		if (fd == 2) {
-			xwrite(fd, data, sz);
-			return sz;
-		}
-		return safe_write(fd, data, sz);
-	}
-	p = data;
-	ssz = sz;
-	while (sz) {
-		unsigned n;
-		char hdr[5];
-
-		n = sz;
-		if (PACKET_MAX - 5 < n)
-			n = PACKET_MAX - 5;
-		sprintf(hdr, "%04x", n + 5);
-		hdr[4] = fd;
-		safe_write(1, hdr, 5);
-		safe_write(1, p, n);
-		p += n;
-		sz -= n;
+	if (use_sideband)
+		return send_sideband(1, fd, data, sz, DEFAULT_PACKET_MAX);
+
+	if (fd == 3)
+		/* emergency quit */
+		fd = 2;
+	if (fd == 2) {
+		xwrite(fd, data, sz);
+		return sz;
 	}
-	return ssz;
+	return safe_write(fd, data, sz);
 }
 
 static void create_pack_file(void)
@@ -308,7 +283,8 @@ static void create_pack_file(void)
 				goto fail;
 			fprintf(stderr, "flushed.\n");
 		}
-		send_client_data(1, NULL, 0);
+		if (use_sideband)
+			packet_flush(1);
 		return;
 	}
  fail: