diff --git a/evennia/commands/default/player.py b/evennia/commands/default/player.py
index 55aab5eb2d..734bc45c3d 100644
--- a/evennia/commands/default/player.py
+++ b/evennia/commands/default/player.py
@@ -416,8 +416,14 @@ class CmdOption(MuxPlayerCommand):
             # change encoding
             old_encoding = self.session.encoding
             new_encoding = self.rhs.strip() or "utf-8"
-            self.session.encoding = new_encoding
-            self.caller.msg("Encoding was changed from %s to %s." % (old_encoding, new_encoding))
+            try:
+                utils.to_str(utils.to_unicode("test-string"), encoding=new_encoding)
+            except LookupError:
+                string = "|rThe encoding '|w%s|r' is invalid. Keeping the previous encoding '|w%s|r'.|n" % (new_encoding, old_encoding)
+            else:
+                self.session.encoding = new_encoding
+                string = "Encoding was changed from '|w%s|n' to '|w%s|n'." % (old_encoding, new_encoding)
+            self.caller.msg(string)
             return
 
         if self.lhs == "screenreader":
diff --git a/evennia/commands/default/unloggedin.py b/evennia/commands/default/unloggedin.py
index 051bab4f3b..7a28eacd61 100644
--- a/evennia/commands/default/unloggedin.py
+++ b/evennia/commands/default/unloggedin.py
@@ -482,8 +482,13 @@ class CmdUnconnectedEncoding(MuxCommand):
             # change encoding
             old_encoding = self.session.encoding
             encoding = self.args
-            self.session.encoding = encoding
-            string = "Your custom text encoding was changed from '%s' to '%s'." % (old_encoding, encoding)
+            try:
+                utils.to_str(utils.to_unicode("test-string"), encoding=encoding)
+            except LookupError:
+                string = "|rThe encoding '|w%s|r' is invalid. Keeping the previous encoding '|w%s|r'.|n" % (encoding, old_encoding)
+            else:
+                self.session.encoding = encoding
+                string = "Your custom text encoding was changed from '|w%s|n' to '|w%s|n'." % (old_encoding, encoding)
         self.caller.msg(string.strip())
 
 class CmdUnconnectedScreenreader(MuxCommand):
diff --git a/evennia/server/sessionhandler.py b/evennia/server/sessionhandler.py
index 47b7f90c90..82526dd432 100644
--- a/evennia/server/sessionhandler.py
+++ b/evennia/server/sessionhandler.py
@@ -524,7 +524,13 @@ class ServerSessionHandler(SessionHandler):
         #from evennia.server.profiling.timetrace import timetrace
         #text = timetrace(text, "ServerSessionHandler.data_out")
 
-        text = text and to_str(to_unicode(text), encoding=session.encoding)
+        try:
+            text = text and to_str(to_unicode(text), encoding=session.encoding)
+        except LookupError:
+            # wrong encoding set on the session. Set it to a safe one
+            session.encoding = "utf-8"
+            text = to_str(to_unicode(text), encoding=session.encoding)
+
 
         # send across AMP
         self.server.amp_protocol.send_MsgServer2Portal(session,