diff --git a/doc/src/sgml/client-auth.sgml b/doc/src/sgml/client-auth.sgml
new file mode 100644
index 3b2935c..f7d7b5a
*** a/doc/src/sgml/client-auth.sgml
--- b/doc/src/sgml/client-auth.sgml
*************** omicron         bryanh
*** 1097,1102 ****
--- 1097,1140 ----
       </varlistentry>
  
       <varlistentry>
+       <term><literal>compat_realm</literal></term>
+       <listitem>
+        <para>
+         If set to 1, the domain's SAM-compatible name (also known as the
+         NetBIOS name) is used for the <literal>include_realm</literal>
+         option. This is the default. If set to 0, the true realm name from
+         the Kerberos user principal name is used. Leave this option
+         disabled to maintain compatibility with existing 
+         <filename>pg_ident.conf</filename> files.
+        </para>
+        <para>
+         Do not enable this option unless your server runs under a domain
+         account (this includes virtual service accounts on a domain member
+         system) and all clients authenticating through SSPI are also using
+         domain accounts, or authentication will fail.
+        </para>
+       </listitem>
+      </varlistentry>
+ 
+      <varlistentry>
+       <term><literal>upn_username</literal></term>
+       <listitem>
+        <para>
+         If this option is enabled along with <literal>compat_realm</literal>,
+         the user name from the Kerberos UPN is used for authentication. If
+         it is disabled (the default), the SAM-compatible user name is used.
+         By default, these two names are identical for new user accounts.
+        </para>
+        <para>
+         Note that <application>libpq</> uses the SAM-compatible name if no
+         explicit user name is specified. If you use
+         <application>libpq</> (e.g. through the ODBC driver), you should
+         leave this option disabled.
+        </para>
+       </listitem>
+      </varlistentry>
+ 
+      <varlistentry>
        <term><literal>map</literal></term>
        <listitem>
         <para>
diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
new file mode 100644
index 7f1ae8c..f31b06f
*** a/src/backend/libpq/auth.c
--- b/src/backend/libpq/auth.c
*************** typedef SECURITY_STATUS
*** 155,160 ****
--- 155,165 ----
  			(WINAPI * QUERY_SECURITY_CONTEXT_TOKEN_FN) (
  													   PCtxtHandle, void **);
  static int	pg_SSPI_recvauth(Port *port);
+ static int	pg_SSPI_make_upn(char *accountname,
+ 							 size_t accountnamesize,
+ 							 char *domainname,
+ 							 size_t domainnamesize,
+ 							 bool update_accountname);
  #endif
  
  /*----------------------------------------------------------------
*************** static int
*** 1026,1031 ****
--- 1031,1037 ----
  pg_SSPI_recvauth(Port *port)
  {
  	int			mtype;
+ 	int			status;
  	StringInfoData buf;
  	SECURITY_STATUS r;
  	CredHandle	sspicred;
*************** pg_SSPI_recvauth(Port *port)
*** 1263,1268 ****
--- 1269,1283 ----
  
  	free(tokenuser);
  
+ 	if (!port->hba->compat_realm)
+ 	{
+ 		status = pg_SSPI_make_upn(accountname, sizeof(accountname),
+ 								  domainname, sizeof(domainname),
+ 								  port->hba->upn_username);
+ 		if (status != STATUS_OK)
+ 			return status;
+ 	}
+ 
  	/*
  	 * Compare realm/domain if requested. In SSPI, always compare case
  	 * insensitive.
*************** pg_SSPI_recvauth(Port *port)
*** 1298,1303 ****
--- 1313,1418 ----
  	else
  		return check_usermap(port->hba->usermap, port->user_name, accountname, true);
  }
+ 
+ /*
+  * Replaces the domainname with the Kerberos realm name,
+  * and optionally the accountname with the Kerberos user name.
+  */
+ static int	pg_SSPI_make_upn(char *accountname,
+ 							 size_t accountnamesize,
+ 							 char *domainname,
+ 							 size_t domainnamesize,
+ 							 bool update_accountname)
+ {
+ 	char *samname;
+ 	char *upname = NULL;
+ 	char *p = NULL;
+ 	ULONG upnamesize = 0;
+ 	size_t upnamerealmsize;
+ 	BOOLEAN res;
+ 
+ 	/* Build SAM name (DOMAIN\\user), then translate to UPN
+ 	   (user@kerberos.realm). The realm name is returned in
+ 	   lower case, but that is fine because in SSPI auth,
+ 	   string comparisons are always case-insensitive. */
+ 
+ 	samname = psprintf("%s\\%s", domainname, accountname);
+ 	res = TranslateName(samname, NameSamCompatible, NameUserPrincipal,
+ 						NULL, &upnamesize);
+ 
+ 	if ((!res && GetLastError() != ERROR_INSUFFICIENT_BUFFER)
+ 		|| upnamesize == 0)
+ 	{
+ 		pfree(samname);
+ 		ereport(LOG,
+ 				(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
+ 				 errmsg("could not translate name")));
+ 				 return STATUS_ERROR;
+ 	}
+ 
+ 	/* upnamesize includes the NUL. */
+ 	upname = (char*)palloc(upnamesize);
+ 
+ 	if (!upname)
+ 	{
+ 		pfree(samname);
+ 		ereport(LOG,
+ 				(errcode(ERRCODE_OUT_OF_MEMORY),
+ 				 errmsg("out of memory")));
+ 		return STATUS_ERROR;
+ 	}
+ 
+ 	res = TranslateName(samname, NameSamCompatible, NameUserPrincipal,
+ 						upname, &upnamesize);
+ 
+ 	pfree(samname);
+ 	if (res)
+ 		p = strchr(upname, '@');
+ 
+ 	if (!res || p == NULL)
+ 	{
+ 		pfree(upname);
+ 		ereport(LOG,
+ 				(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
+ 				 errmsg("could not translate name")));
+ 				 return STATUS_ERROR;
+ 	}
+ 
+ 	/* Length of realm name after the '@', including the NUL. */
+ 	upnamerealmsize = upnamesize - (p - upname + 1);
+ 
+ 	/* Replace domainname with realm name. */
+ 	if (upnamerealmsize > domainnamesize)
+ 	{
+ 		pfree(upname);
+ 		ereport(LOG,
+ 				(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
+ 				 errmsg("realm name too long")));
+ 				 return STATUS_ERROR;
+ 	}
+ 
+ 	/* Length is now safe. */
+ 	strcpy(domainname, p+1);
+ 
+ 	/* Replace account name as well (in case UPN != SAM)? */
+ 	if (update_accountname)
+ 	{
+ 		if ((p - upname + 1) > accountnamesize)
+ 		{
+ 			pfree(upname);
+ 			ereport(LOG,
+ 					(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
+ 					 errmsg("translated account name too long")));
+ 					 return STATUS_ERROR;
+ 		}
+ 
+ 		*p = 0;
+ 		strcpy(accountname, upname);
+ 	}
+ 
+ 	pfree(upname);
+ 	return STATUS_OK;
+ }
  #endif   /* ENABLE_SSPI */
  
  
diff --git a/src/backend/libpq/hba.c b/src/backend/libpq/hba.c
new file mode 100644
index 28f9fb5..9ca6925
*** a/src/backend/libpq/hba.c
--- b/src/backend/libpq/hba.c
*************** parse_hba_line(List *line, int line_num,
*** 1287,1292 ****
--- 1287,1302 ----
  		parsedline->auth_method == uaSSPI)
  		parsedline->include_realm = true;
  
+ 	/*
+ 	 * For SSPI, include_realm defaults to the SAM-compatible domain
+ 	 * (aka NetBIOS name) and user names instead of the Kerberos
+ 	 * principal name for compatibility.
+ 	 */
+ 	if (parsedline->auth_method == uaSSPI) {
+ 		parsedline->compat_realm = true;
+ 		parsedline->upn_username = false;
+ 	}
+ 
  	/* Parse remaining arguments */
  	while ((field = lnext(field)) != NULL)
  	{
*************** parse_hba_auth_opt(char *name, char *val
*** 1570,1575 ****
--- 1580,1603 ----
  		else
  			hbaline->include_realm = false;
  	}
+ 	else if (strcmp(name, "compat_realm") == 0)
+ 	{
+ 		if (hbaline->auth_method != uaSSPI)
+ 			INVALID_AUTH_OPTION("compat_realm", gettext_noop("sspi"));
+ 		if (strcmp(val, "1") == 0)
+ 			hbaline->compat_realm = true;
+ 		else
+ 			hbaline->compat_realm = false;
+ 	}
+ 	else if (strcmp(name, "upn_username") == 0)
+ 	{
+ 		if (hbaline->auth_method != uaSSPI)
+ 			INVALID_AUTH_OPTION("upn_username", gettext_noop("sspi"));
+ 		if (strcmp(val, "1") == 0)
+ 			hbaline->upn_username = true;
+ 		else
+ 			hbaline->upn_username = false;
+ 	}
  	else if (strcmp(name, "radiusserver") == 0)
  	{
  		struct addrinfo *gai_result;
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
new file mode 100644
index 68a953a..f3868f7
*** a/src/include/libpq/hba.h
--- b/src/include/libpq/hba.h
*************** typedef struct HbaLine
*** 77,82 ****
--- 77,84 ----
  	bool		clientcert;
  	char	   *krb_realm;
  	bool		include_realm;
+ 	bool		compat_realm;
+ 	bool		upn_username;
  	char	   *radiusserver;
  	char	   *radiussecret;
  	char	   *radiusidentifier;