diff --git a/ChangeLog.asciidoc b/ChangeLog.asciidoc
index 06b83b6a4..3dcf80c21 100644
--- a/ChangeLog.asciidoc
+++ b/ChangeLog.asciidoc
@@ -46,7 +46,8 @@ https://weechat.org/files/releasenotes/ReleaseNotes-devel.html[release notes]
 * core: fix truncated messages after a word with a length of zero on screen
   (for example a zero width space: U+200B) (bug #40985, issue #502)
 * api: fix handle of invalid escape in function string_convert_escaped_chars()
-* irc: add a missing colon before the password in PASS message (issue #602)
+* irc: add a missing colon before the password in PASS message, if the password
+  has spaces or begins with a colon (issue #602)
 * irc: fix charset decoding in incoming private messages (issue #520)
 * irc: display the arrow before server name in raw buffer
 * irc: fix display of messages sent to server in raw buffer
diff --git a/src/plugins/irc/irc-server.c b/src/plugins/irc/irc-server.c
index 678236200..b81434787 100644
--- a/src/plugins/irc/irc-server.c
+++ b/src/plugins/irc/irc-server.c
@@ -3328,7 +3328,13 @@ irc_server_login (struct t_irc_server *server)
         server, IRC_SERVER_OPTION_CAPABILITIES);
 
     if (password && password[0])
-        irc_server_sendf (server, 0, NULL, "PASS :%s", password);
+    {
+        irc_server_sendf (
+            server, 0, NULL,
+            "PASS %s%s",
+            ((password[0] == ':') || (strchr (password, ' '))) ? ":" : "",
+            password);
+    }
 
     if (!server->nick)
     {