diff --git a/lib/socket-util.c b/lib/socket-util.c
index 8949da77d..206e17bd2 100644
--- a/lib/socket-util.c
+++ b/lib/socket-util.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -101,11 +101,14 @@ setsockopt_tcp_nodelay(int fd)
     }
 }
 
+/* Sets the DSCP value of socket 'fd' to 'dscp', which must be 63 or less.
+ * 'family' must indicate the socket's address family (AF_INET or AF_INET6, to
+ * do anything useful). */
 int
-set_dscp(int fd, uint8_t dscp)
+set_dscp(int fd, int family, uint8_t dscp)
 {
+    int retval;
     int val;
-    bool success;
 
 #ifdef _WIN32
     /* XXX: Consider using QoS2 APIs for Windows to set dscp. */
@@ -115,29 +118,22 @@ set_dscp(int fd, uint8_t dscp)
     if (dscp > 63) {
         return EINVAL;
     }
-
-    /* Note: this function is used for both of IPv4 and IPv6 sockets */
-    success = false;
     val = dscp << 2;
-    if (setsockopt(fd, IPPROTO_IP, IP_TOS, &val, sizeof val)) {
-        if (sock_errno() != ENOPROTOOPT) {
-            return sock_errno();
-        }
-    } else {
-        success = true;
-    }
-    if (setsockopt(fd, IPPROTO_IPV6, IPV6_TCLASS, &val, sizeof val)) {
-        if (sock_errno() != ENOPROTOOPT) {
-            return sock_errno();
-        }
-    } else {
-        success = true;
-    }
-    if (!success) {
+
+    switch (family) {
+    case AF_INET:
+        retval = setsockopt(fd, IPPROTO_IP, IP_TOS, &val, sizeof val);
+        break;
+
+    case AF_INET6:
+        retval = setsockopt(fd, IPPROTO_IPV6, IPV6_TCLASS, &val, sizeof val);
+        break;
+
+    default:
         return ENOPROTOOPT;
     }
 
-    return 0;
+    return retval ? sock_errno() : 0;
 }
 
 /* Translates 'host_name', which must be a string representation of an IP
@@ -470,7 +466,7 @@ inet_open_active(int style, const char *target, uint16_t default_port,
     /* The dscp bits must be configured before connect() to ensure that the
      * TOS field is set during the connection establishment.  If set after
      * connect(), the handshake SYN frames will be sent with a TOS of 0. */
-    error = set_dscp(fd, dscp);
+    error = set_dscp(fd, ss.ss_family, dscp);
     if (error) {
         VLOG_ERR("%s: set_dscp: %s", target, sock_strerror(error));
         goto exit;
@@ -611,7 +607,7 @@ inet_open_passive(int style, const char *target, int default_port,
     /* The dscp bits must be configured before connect() to ensure that the TOS
      * field is set during the connection establishment.  If set after
      * connect(), the handshake SYN frames will be sent with a TOS of 0. */
-    error = set_dscp(fd, dscp);
+    error = set_dscp(fd, ss.ss_family, dscp);
     if (error) {
         VLOG_ERR("%s: set_dscp: %s", target, sock_strerror(error));
         goto error;
diff --git a/lib/socket-util.h b/lib/socket-util.h
index 5b94f206d..1178fb8ce 100644
--- a/lib/socket-util.h
+++ b/lib/socket-util.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,7 +30,7 @@
 int set_nonblocking(int fd);
 void xset_nonblocking(int fd);
 void setsockopt_tcp_nodelay(int fd);
-int set_dscp(int fd, uint8_t dscp);
+int set_dscp(int fd, int family, uint8_t dscp);
 
 int lookup_ip(const char *host_name, struct in_addr *address);
 int lookup_ipv6(const char *host_name, struct in6_addr *address);
diff --git a/python/ovs/socket_util.py b/python/ovs/socket_util.py
index 1af6474b0..f657d11c8 100644
--- a/python/ovs/socket_util.py
+++ b/python/ovs/socket_util.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2010, 2012, 2014 Nicira, Inc.
+# Copyright (c) 2010, 2012, 2014, 2015 Nicira, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -213,14 +213,16 @@ def inet_open_active(style, target, default_port, dscp):
         is_addr_inet = is_valid_ipv4_address(address[0])
         if is_addr_inet:
             sock = socket.socket(socket.AF_INET, style, 0)
+            family = socket.AF_INET
         else:
             sock = socket.socket(socket.AF_INET6, style, 0)
+            family = socket.AF_INET6
     except socket.error, e:
         return get_exception_errno(e), None
 
     try:
         set_nonblocking(sock)
-        set_dscp(sock, dscp)
+        set_dscp(sock, family, dscp)
         try:
             sock.connect(address)
         except socket.error, e:
@@ -292,21 +294,20 @@ def set_nonblocking(sock):
                  % os.strerror(get_exception_errno(e)))
 
 
-def set_dscp(sock, dscp):
+def set_dscp(sock, family, dscp):
     if dscp > 63:
         raise ValueError("Invalid dscp %d" % dscp)
 
-    # Note: this function is used for both of IPv4 and IPv6 sockets
-    success = False
     val = dscp << 2
-    try:
-        sock.setsockopt(socket.IPPROTO_IP, socket.IP_TOS, val)
-    except socket.error, e:
-        if get_exception_errno(e) != errno.ENOPROTOOPT:
+    if family == socket.AF_INET:
+        try:
+            sock.setsockopt(socket.IPPROTO_IP, socket.IP_TOS, val)
+        except socket.error, e:
             raise
-    success = True
-    try:
-        sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_TCLASS, val)
-    except socket.error, e:
-        if get_exception_errno(e) != errno.ENOPROTOOPT or not success:
+    elif family == socket.AF_INET6:
+        try:
+            sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_TCLASS, val)
+        except socket.error, e:
             raise
+    else:
+        raise