diff --git a/ChangeLog.adoc b/ChangeLog.adoc
index ae69681d3..4fcd20d1a 100644
--- a/ChangeLog.adoc
+++ b/ChangeLog.adoc
@@ -62,7 +62,7 @@ Bug fixes::
   * irc: update autojoin option with redirected channels when autojoin_dynamic is enabled (issue #1898)
   * irc: don't switch to buffer of joined channel if it was not manually joined nor present in server autojoin option
   * irc: fix target buffer for commands 432/433 (erroneous nickname/nickname already in use) when the nickname looks like a channel
-  * irc: add message 415 (cannot send message to channel)
+  * irc: add messages 415 (cannot send message to channel) and 742 (mode cannot be set)
   * lua: fix crash with print when the value to print is not a string (issue #1904, issue #1905)
   * spell: check buffer pointer received in info "spell_dict"
   * typing: fix crash when pointer buffer is not received in callback for signal "input_text_changed" (issue #1869)
diff --git a/src/plugins/irc/irc-protocol.c b/src/plugins/irc/irc-protocol.c
index 8439cc674..56ccbacd5 100644
--- a/src/plugins/irc/irc-protocol.c
+++ b/src/plugins/irc/irc-protocol.c
@@ -7608,6 +7608,7 @@ irc_protocol_recv_command (struct t_irc_server *server,
         IRCB(732, 1, 0, 732),            /* list of monitored nicks         */
         IRCB(733, 1, 0, 733),            /* end of monitor list             */
         IRCB(734, 1, 0, 734),            /* monitor list is full            */
+        IRCB(742, 1, 0, generic_error),  /* mode cannot be set              */
         IRCB(900, 1, 0, 900),            /* logged in as (SASL)             */
         IRCB(901, 1, 0, 901),            /* you are now logged out          */
         IRCB(902, 1, 0, sasl_end_fail),  /* SASL auth failed (acc. locked)  */
diff --git a/tests/unit/plugins/irc/test-irc-protocol.cpp b/tests/unit/plugins/irc/test-irc-protocol.cpp
index ca6bced25..2965f9de8 100644
--- a/tests/unit/plugins/irc/test-irc-protocol.cpp
+++ b/tests/unit/plugins/irc/test-irc-protocol.cpp
@@ -4428,6 +4428,33 @@ TEST(IrcProtocolWithServer, 734)
     CHECK_SRV("=!= Monitor list is full (10)");
 }
 
+/*
+ * Tests functions:
+ *   irc_protocol_cb_742 (mode cannot be set)
+ */
+
+TEST(IrcProtocolWithServer, 742)
+{
+    SRV_INIT_JOIN;
+
+    /* not enough parameters */
+    RECV(":server 742");
+    CHECK_ERROR_PARAMS("742", 0, 2);
+    RECV(":server 742 alice");
+    CHECK_ERROR_PARAMS("742", 1, 2);
+
+    RECV(":server 742 alice #test");
+    CHECK_SRV("-- #test");
+    RECV(":server 742 alice #test n nstlk :MODE cannot be set due to channel "
+         "having an active MLOCK restriction policy");
+    CHECK_CHAN("-- #test: n nstlk MODE cannot be set due to channel having "
+               "an active MLOCK restriction policy");
+    RECV(":server 742 alice #test2 n nstlk :MODE cannot be set due to channel "
+         "having an active MLOCK restriction policy");
+    CHECK_SRV("-- #test2: n nstlk MODE cannot be set due to channel having "
+               "an active MLOCK restriction policy");
+}
+
 /*
  * Tests functions:
  *   irc_protocol_cb_900 (logged in as (SASL))