diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 6d2e86a1f59..2e0c06102ee 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -232,6 +232,11 @@ PGconn *PQsetdbLogin(const char *pghost,
         if it had been passed to <xref linkend="libpq-PQconnectdb"/>, and the remaining
         parameters are then applied as specified for <xref linkend="libpq-PQconnectdbParams"/>.
       </para>
+
+      <para>
+        <literal>pgtty</literal> is no longer used and any value passed will
+        be ignored.
+      </para>
      </listitem>
     </varlistentry>
 
@@ -2119,10 +2124,10 @@ char *PQport(const PGconn *conn);
 
      <listitem>
       <para>
-       Returns the debug <acronym>TTY</acronym> of the connection.
-       (This is obsolete, since the server no longer pays attention
-       to the <acronym>TTY</acronym> setting, but the function remains
-       for backward compatibility.)
+       This function no longer does anything, but it remains for backwards
+       compatibility.  The function always return an empty string, or
+       <symbol>NULL</symbol> if the <parameter>conn</parameter> argument is
+       <symbol>NULL</symbol>.
 
 <synopsis>
 char *PQtty(const PGconn *conn);
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index a294d293ebe..aeb64c5bca3 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -120,9 +120,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
  * by environment variables
  */
 #define DefaultHost		"localhost"
-#define DefaultTty		""
 #define DefaultOption	""
-#define DefaultAuthtype		  ""
 #ifdef USE_SSL
 #define DefaultChannelBinding	"prefer"
 #else
@@ -192,14 +190,6 @@ typedef struct _internalPQconninfoOption
 } internalPQconninfoOption;
 
 static const internalPQconninfoOption PQconninfoOptions[] = {
-	/*
-	 * "authtype" is no longer used, so mark it "don't show".  We keep it in
-	 * the array so as not to reject conninfo strings from old apps that might
-	 * still try to set it.
-	 */
-	{"authtype", "PGAUTHTYPE", DefaultAuthtype, NULL,
-	"Database-Authtype", "D", 20, -1},
-
 	{"service", "PGSERVICE", NULL, NULL,
 	"Database-Service", "", 20, -1},
 
@@ -243,14 +233,6 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Client-Encoding", "", 10,
 	offsetof(struct pg_conn, client_encoding_initial)},
 
-	/*
-	 * "tty" is no longer used either, but keep it present for backwards
-	 * compatibility.
-	 */
-	{"tty", "PGTTY", DefaultTty, NULL,
-		"Backend-Debug-TTY", "D", 40,
-	offsetof(struct pg_conn, pgtty)},
-
 	{"options", "PGOPTIONS", DefaultOption, NULL,
 		"Backend-Options", "", 40,
 	offsetof(struct pg_conn, pgoptions)},
@@ -1581,15 +1563,6 @@ PQsetdbLogin(const char *pghost, const char *pgport, const char *pgoptions,
 			goto oom_error;
 	}
 
-	if (pgtty && pgtty[0] != '\0')
-	{
-		if (conn->pgtty)
-			free(conn->pgtty);
-		conn->pgtty = strdup(pgtty);
-		if (!conn->pgtty)
-			goto oom_error;
-	}
-
 	if (login && login[0] != '\0')
 	{
 		if (conn->pguser)
@@ -4031,8 +4004,6 @@ freePGconn(PGconn *conn)
 		free(conn->pghostaddr);
 	if (conn->pgport)
 		free(conn->pgport);
-	if (conn->pgtty)
-		free(conn->pgtty);
 	if (conn->connect_timeout)
 		free(conn->connect_timeout);
 	if (conn->pgtcp_user_timeout)
@@ -6633,12 +6604,16 @@ PQport(const PGconn *conn)
 	return "";
 }
 
+/*
+ * No longer does anything, but the function remains for API backwards
+ * compatibility.
+ */
 char *
 PQtty(const PGconn *conn)
 {
 	if (!conn)
 		return NULL;
-	return conn->pgtty;
+	return "";
 }
 
 char *
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index cca98c14bf8..0965c5ac511 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -338,8 +338,6 @@ struct pg_conn
 								 * precedence over pghost. */
 	char	   *pgport;			/* the server's communication port number, or
 								 * a comma-separated list of ports */
-	char	   *pgtty;			/* tty on which the backend messages is
-								 * displayed (OBSOLETE, NOT USED) */
 	char	   *connect_timeout;	/* connection timeout (numeric string) */
 	char	   *pgtcp_user_timeout; /* tcp user timeout (numeric string) */
 	char	   *client_encoding_initial;	/* encoding to use */
diff --git a/src/test/examples/testlibpq4.c b/src/test/examples/testlibpq4.c
index dd11bbc46dc..da4443072da 100644
--- a/src/test/examples/testlibpq4.c
+++ b/src/test/examples/testlibpq4.c
@@ -50,8 +50,7 @@ main(int argc, char **argv)
 {
 	char	   *pghost,
 			   *pgport,
-			   *pgoptions,
-			   *pgtty;
+			   *pgoptions;
 	char	   *dbName1,
 			   *dbName2;
 	char	   *tblName;
@@ -88,13 +87,12 @@ main(int argc, char **argv)
 	pgport = NULL;				/* port of the backend */
 	pgoptions = NULL;			/* special options to start up the backend
 								 * server */
-	pgtty = NULL;				/* debugging tty for the backend */
 
 	/* make a connection to the database */
-	conn1 = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName1);
+	conn1 = PQsetdb(pghost, pgport, pgoptions, NULL, dbName1);
 	check_prepare_conn(conn1, dbName1);
 
-	conn2 = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName2);
+	conn2 = PQsetdb(pghost, pgport, pgoptions, NULL, dbName2);
 	check_prepare_conn(conn2, dbName2);
 
 	/* start a transaction block */