diff --git a/RELNOTES b/RELNOTES
index 466a5dbf..6a67baa0 100644
--- a/RELNOTES
+++ b/RELNOTES
@@ -49,6 +49,8 @@ work on other platforms. Please report any problems and suggested fixes to
 - Added client support for setting interface MTU and metric, thanks to
   Roy "UberLord" Marples <roy@marples.name>.
 
+- Added client -D option to specify DUID type to send.
+
 			Changes since 4.1.0 (bug fixes)
 
 - Remove infinite loop in token_print_indent_concat().
diff --git a/client/dhc6.c b/client/dhc6.c
index b9f79af7..dc48c465 100644
--- a/client/dhc6.c
+++ b/client/dhc6.c
@@ -143,15 +143,18 @@ form_duid(struct data_string *duid, const char *file, int line)
 	    (ip->hw_address.hlen > sizeof(ip->hw_address.hbuf)))
 		log_fatal("Impossible hardware address length at %s:%d.", MDL);
 
+	if (duid_type == 0)
+		duid_type = stateless ? DUID_LL : DUID_LLT;
+
 	/*
 	 * 2 bytes for the 'duid type' field.
 	 * 2 bytes for the 'htype' field.
-	 * (not stateless) 4 bytes for the 'current time'.
+	 * (DUID_LLT) 4 bytes for the 'current time'.
 	 * enough bytes for the hardware address (note that hw_address has
 	 * the 'htype' on byte zero).
 	 */
 	len = 4 + (ip->hw_address.hlen - 1);
-	if (!stateless)
+	if (duid_type == DUID_LLT)
 		len += 4;
 	if (!buffer_allocate(&duid->buffer, len, MDL))
 		log_fatal("no memory for default DUID!");
@@ -159,7 +162,7 @@ form_duid(struct data_string *duid, const char *file, int line)
 	duid->len = len;
 
 	/* Basic Link Local Address type of DUID. */
-	if (!stateless) {
+	if (duid_type == DUID_LLT) {
 		putUShort(duid->buffer->data, DUID_LLT);
 		putUShort(duid->buffer->data + 2, ip->hw_address.hbuf[0]);
 		putULong(duid->buffer->data + 4, cur_time - DUID_TIME_EPOCH);
diff --git a/client/dhclient.8 b/client/dhclient.8
index 4437b9b4..cdd6c9ba 100644
--- a/client/dhclient.8
+++ b/client/dhclient.8
@@ -1,4 +1,4 @@
-.\"	$Id: dhclient.8,v 1.30 2008/11/20 14:55:14 jreed Exp $
+.\"	$Id: dhclient.8,v 1.31 2009/05/27 20:11:38 pselkirk Exp $
 .\"
 .\" Copyright (c) 2004,2007-2008 by Internet Systems Consortium, Inc. ("ISC")
 .\" Copyright (c) 1996-2003 by Internet Software Consortium
@@ -56,6 +56,10 @@ dhclient - Dynamic Host Configuration Protocol Client
 ]
 ]
 [
+.B -D
+.I LL|LLT
+]
+[
 .B -p
 .I port
 ]
@@ -138,10 +142,14 @@ important details about the network to which it is attached, such as
 the location of a default router, the location of a name server, and
 so on.
 .PP
-If given the -4 command line argument (default), dhclient will use the
+If given the 
+.B -4
+command line argument (default), dhclient will use the
 DHCPv4 protocol to obtain an IPv4 address and configuration parameters.
 .PP
-If given the -6 command line argument, dhclient will use the DHCPv6
+If given the
+.B -6
+command line argument, dhclient will use the DHCPv6
 protocol to obtain whatever IPv6 addresses are available along with
 configuration parameters. But with
 .B -S
@@ -161,7 +169,17 @@ address query,
 restores it. Note it is not recommended to mix queries of different types
 together, or even to share the lease file between them.
 .PP
-If given the --version command line argument, dhclient will print its
+By default, DHCPv6 dhclient creates an identifier based on the
+link-layer address (DUID-LL) if it is running in stateless mode (with
+-S, not requesting an address), or it creates an identifier based on
+the link-layer address plus a timestamp (DUID-LLT) if it is running in
+stateful mode (without -S, requesting an address).
+.B -D
+overrides this default, with a value of either "LL" or "LLT".
+.PP
+If given the 
+.B --version
+command line argument, dhclient will print its
 version number and exit.
 .PP
 On startup, dhclient reads the
diff --git a/client/dhclient.c b/client/dhclient.c
index dcd294a8..580c7126 100644
--- a/client/dhclient.c
+++ b/client/dhclient.c
@@ -57,6 +57,7 @@ struct in_addr inaddr_any;
 struct sockaddr_in sockaddr_broadcast;
 struct in_addr giaddr;
 struct data_string default_duid;
+int duid_type = 0;
 
 /* ASSERT_STATE() does nothing now; it used to be
    assert (state_is == state_shouldbe). */
@@ -268,6 +269,21 @@ main(int argc, char **argv) {
 				wanted_ia_na = 0;
 			}
 			wanted_ia_pd++;
+		} else if (!strcmp(argv[i], "-D")) {
+			if (local_family_set && (local_family == AF_INET)) {
+				usage();
+			}
+			local_family_set = 1;
+			local_family = AF_INET6;
+			if (++i == argc)
+				usage();
+			if (!strcasecmp(argv[i], "LL")) {
+				duid_type = DUID_LL;
+			} else if (!strcasecmp(argv[i], "LLT")) {
+				duid_type = DUID_LLT;
+			} else {
+				usage();
+			}
 #endif /* DHCPv6 */
 		} else if (!strcmp(argv[i], "-v")) {
 			quiet = 0;
@@ -651,7 +667,7 @@ static void usage()
 
 	log_error("Usage: dhclient %s %s",
 #ifdef DHCPv6
-		  "[-4|-6] [-SNTP1dvrx] [-nw] [-p <port>]",
+		  "[-4|-6] [-SNTP1dvrx] [-nw] [-p <port>] [-D LL|LLT]",
 #else /* DHCPv6 */
 		  "[-1dvrx] [-nw] [-p <port>]",
 #endif /* DHCPv6 */
diff --git a/includes/dhcpd.h b/includes/dhcpd.h
index 22db8aea..b0c4969d 100644
--- a/includes/dhcpd.h
+++ b/includes/dhcpd.h
@@ -2471,6 +2471,7 @@ extern const char *path_dhclient_pid;
 extern char *path_dhclient_script;
 extern int interfaces_requested;
 extern struct data_string default_duid;
+extern int duid_type;
 
 extern struct client_config top_level_config;