diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 403f7010..3b53933f 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -1243,7 +1243,7 @@ static const struct ifa_flag_data_t {
 	{ .name = "secondary",		.mask = IFA_F_SECONDARY,	.readonly = true,	.v6only = false},
 	{ .name = "temporary",		.mask = IFA_F_SECONDARY,	.readonly = true,	.v6only = false},
 	{ .name = "nodad",		.mask = IFA_F_NODAD,	 	.readonly = false,	.v6only = true},
-	{ .name = "optimistic",		.mask = IFA_F_OPTIMISTIC,	.readonly = true,	.v6only = true},
+	{ .name = "optimistic",		.mask = IFA_F_OPTIMISTIC,	.readonly = false,	.v6only = true},
 	{ .name = "dadfailed",		.mask = IFA_F_DADFAILED,	.readonly = true,	.v6only = true},
 	{ .name = "home",		.mask = IFA_F_HOMEADDRESS,	.readonly = false,	.v6only = true},
 	{ .name = "deprecated",		.mask = IFA_F_DEPRECATED,	.readonly = true,	.v6only = true},
diff --git a/man/man8/ip-address.8.in b/man/man8/ip-address.8.in
index 2a553190..fe773c91 100644
--- a/man/man8/ip-address.8.in
+++ b/man/man8/ip-address.8.in
@@ -92,7 +92,7 @@ ip-address \- protocol address management
 
 .ti -8
 .IR CONFFLAG " := "
-.RB "[ " home " | " mngtmpaddr " | " nodad " | " noprefixroute " | " autojoin " ]"
+.RB "[ " home " | " mngtmpaddr " | " nodad " | " optimstic " | " noprefixroute " | " autojoin " ]"
 
 .ti -8
 .IR LIFETIME " := [ "
@@ -258,6 +258,11 @@ stateless auto-configuration was active.
 (IPv6 only) do not perform Duplicate Address Detection (RFC 4862) when
 adding this address.
 
+.TP
+.B optimistic
+(IPv6 only) When performing Duplicate Address Detection, use the RFC 4429
+optimistic variant.
+
 .TP
 .B noprefixroute
 Do not automatically create a route for the network prefix of the added