diff --git a/ldisc.c b/ldisc.c
index e5e1449d..8c985f06 100644
--- a/ldisc.c
+++ b/ldisc.c
@@ -139,6 +139,10 @@ void ldisc_echoedit_update(Ldisc *ldisc)
     seat_echoedit_update(ldisc->seat, ECHOING, EDITING);
 }
 
+void ldisc_check_sendok(Ldisc *ldisc)
+{
+}
+
 void ldisc_send(Ldisc *ldisc, const void *vbuf, int len, bool interactive)
 {
     const char *buf = (const char *)vbuf;
diff --git a/otherbackends/raw.c b/otherbackends/raw.c
index 87a136ba..97b7be09 100644
--- a/otherbackends/raw.c
+++ b/otherbackends/raw.c
@@ -17,6 +17,7 @@ struct Raw {
     size_t bufsize;
     Seat *seat;
     LogContext *logctx;
+    Ldisc *ldisc;
     bool sent_console_eof, sent_socket_eof, socket_connected;
 
     Conf *conf;
@@ -41,6 +42,8 @@ static void raw_log(Plug *plug, PlugLogType type, SockAddr *addr, int port,
                        error_code, raw->conf, raw->socket_connected);
     if (type == PLUGLOG_CONNECT_SUCCESS) {
         raw->socket_connected = true;
+        if (raw->ldisc)
+            ldisc_check_sendok(raw->ldisc);
         if (is_tempseat(raw->seat)) {
             Seat *ts = raw->seat;
             tempseat_flush(ts);
@@ -295,7 +298,8 @@ static bool raw_ldisc(Backend *be, int option)
 
 static void raw_provide_ldisc(Backend *be, Ldisc *ldisc)
 {
-    /* This is a stub. */
+    Raw *raw = container_of(be, Raw, backend);
+    raw->ldisc = ldisc;
 }
 
 static int raw_exitcode(Backend *be)
diff --git a/otherbackends/rlogin.c b/otherbackends/rlogin.c
index 51e6ed05..11deb89c 100644
--- a/otherbackends/rlogin.c
+++ b/otherbackends/rlogin.c
@@ -22,6 +22,7 @@ struct Rlogin {
     int term_width, term_height;
     Seat *seat;
     LogContext *logctx;
+    Ldisc *ldisc;
 
     Conf *conf;
 
@@ -194,6 +195,8 @@ static void rlogin_startup(Rlogin *rlogin, int prompt_result,
     }
 
     rlogin->prompt = NULL;
+    if (rlogin->ldisc)
+        ldisc_check_sendok(rlogin->ldisc);
 }
 
 static const PlugVtable Rlogin_plugvt = {
@@ -413,7 +416,8 @@ static bool rlogin_ldisc(Backend *be, int option)
 
 static void rlogin_provide_ldisc(Backend *be, Ldisc *ldisc)
 {
-    /* This is a stub. */
+    Rlogin *rlogin = container_of(be, Rlogin, backend);
+    rlogin->ldisc = ldisc;
 }
 
 static int rlogin_exitcode(Backend *be)
diff --git a/otherbackends/supdup.c b/otherbackends/supdup.c
index ae7e67f7..a3418fe1 100644
--- a/otherbackends/supdup.c
+++ b/otherbackends/supdup.c
@@ -71,6 +71,7 @@ struct supdup_tag
 
     Seat *seat;
     LogContext *logctx;
+    Ldisc *ldisc;
     int term_width, term_height;
 
     long long ttyopt;
@@ -565,6 +566,8 @@ static void supdup_log(Plug *plug, PlugLogType type, SockAddr *addr, int port,
                        supdup->conf, supdup->socket_connected);
     if (type == PLUGLOG_CONNECT_SUCCESS) {
         supdup->socket_connected = true;
+        if (supdup->ldisc)
+            ldisc_check_sendok(supdup->ldisc);
         if (is_tempseat(supdup->seat)) {
             Seat *ts = supdup->seat;
             tempseat_flush(ts);
@@ -893,6 +896,8 @@ static bool supdup_ldisc(Backend *be, int option)
 
 static void supdup_provide_ldisc(Backend *be, Ldisc *ldisc)
 {
+    Supdup *supdup = container_of(be, Supdup, backend);
+    supdup->ldisc = ldisc;
 }
 
 static int supdup_exitcode(Backend *be)
diff --git a/otherbackends/telnet.c b/otherbackends/telnet.c
index 540d384c..98c202c6 100644
--- a/otherbackends/telnet.c
+++ b/otherbackends/telnet.c
@@ -628,6 +628,8 @@ static void telnet_log(Plug *plug, PlugLogType type, SockAddr *addr, int port,
                        telnet->socket_connected);
     if (type == PLUGLOG_CONNECT_SUCCESS) {
         telnet->socket_connected = true;
+        if (telnet->ldisc)
+            ldisc_check_sendok(telnet->ldisc);
         if (is_tempseat(telnet->seat)) {
             Seat *ts = telnet->seat;
             tempseat_flush(ts);
diff --git a/pscp.c b/pscp.c
index ec4dfa8a..7717d8d6 100644
--- a/pscp.c
+++ b/pscp.c
@@ -58,6 +58,7 @@ const char *const appname = "PSCP";
 #define MAX_SCP_BUFSIZE 16384
 
 void ldisc_echoedit_update(Ldisc *ldisc) { }
+void ldisc_check_sendok(Ldisc *ldisc) { }
 
 static size_t pscp_output(Seat *, bool is_stderr, const void *, size_t);
 static bool pscp_eof(Seat *);
diff --git a/psftp.c b/psftp.c
index 16beee56..a09837c7 100644
--- a/psftp.c
+++ b/psftp.c
@@ -2448,6 +2448,7 @@ int do_sftp(int mode, int modeflags, char *batchfile)
 static bool verbose = false;
 
 void ldisc_echoedit_update(Ldisc *ldisc) { }
+void ldisc_check_sendok(Ldisc *ldisc) { }
 
 /*
  * Receive a block of data from the SSH link. Block until all data
diff --git a/putty.h b/putty.h
index 8b419a32..fcfff4b6 100644
--- a/putty.h
+++ b/putty.h
@@ -2055,6 +2055,7 @@ void ldisc_configure(Ldisc *, Conf *);
 void ldisc_free(Ldisc *);
 void ldisc_send(Ldisc *, const void *buf, int len, bool interactive);
 void ldisc_echoedit_update(Ldisc *);
+void ldisc_check_sendok(Ldisc *);
 
 /*
  * Exports from sshrand.c.
diff --git a/ssh.h b/ssh.h
index 23bed390..34a8909d 100644
--- a/ssh.h
+++ b/ssh.h
@@ -397,6 +397,7 @@ LogContext *ssh_get_logctx(Ssh *ssh);
 void ssh_throttle_conn(Ssh *ssh, int adjust);
 void ssh_got_exitcode(Ssh *ssh, int status);
 void ssh_ldisc_update(Ssh *ssh);
+void ssh_check_sendok(Ssh *ssh);
 void ssh_got_fallback_cmd(Ssh *ssh);
 bool ssh_is_bare(Ssh *ssh);
 
diff --git a/ssh/connection1.c b/ssh/connection1.c
index 7b1765f6..071e0139 100644
--- a/ssh/connection1.c
+++ b/ssh/connection1.c
@@ -775,6 +775,8 @@ static void ssh1_set_wants_user_input(ConnectionLayer *cl, bool wanted)
 
     s->want_user_input = wanted;
     s->finished_setup = true;
+    if (wanted)
+        ssh_check_sendok(s->ppl.ssh);
 }
 
 static bool ssh1_connection_want_user_input(PacketProtocolLayer *ppl)
diff --git a/ssh/connection2.c b/ssh/connection2.c
index 2e7102db..86e26f4b 100644
--- a/ssh/connection2.c
+++ b/ssh/connection2.c
@@ -1709,6 +1709,8 @@ static void ssh2_set_wants_user_input(ConnectionLayer *cl, bool wanted)
         container_of(cl, struct ssh2_connection_state, cl);
 
     s->want_user_input = wanted;
+    if (wanted)
+        ssh_check_sendok(s->ppl.ssh);
 }
 
 static bool ssh2_connection_want_user_input(PacketProtocolLayer *ppl)
diff --git a/ssh/server.c b/ssh/server.c
index 1517522b..a3c400c0 100644
--- a/ssh/server.c
+++ b/ssh/server.c
@@ -244,6 +244,8 @@ Conf *make_ssh_server_conf(void)
     return conf;
 }
 
+void ssh_check_sendok(Ssh *ssh) {}
+
 static const PlugVtable ssh_server_plugvt = {
     .log = server_socket_log,
     .closing = server_closing,
diff --git a/ssh/ssh.c b/ssh/ssh.c
index 98b7a68a..10c52001 100644
--- a/ssh/ssh.c
+++ b/ssh/ssh.c
@@ -1156,6 +1156,14 @@ static bool ssh_sendok(Backend *be)
     return ssh->base_layer && ssh_ppl_want_user_input(ssh->base_layer);
 }
 
+void ssh_check_sendok(Ssh *ssh)
+{
+    /* Called when the connection layer might have caused ssh_sendok
+     * to start returning true */
+    if (ssh->ldisc)
+        ldisc_check_sendok(ssh->ldisc);
+}
+
 void ssh_ldisc_update(Ssh *ssh)
 {
     /* Called when the connection layer wants to propagate an update