diff --git a/src/plwm.pl b/src/plwm.pl
index 059bf97..9c608f1 100644
--- a/src/plwm.pl
+++ b/src/plwm.pl
@@ -1648,9 +1648,16 @@
 			% Update geometry if it changed
 			global_key_value(monitor_geom, Output, PrevGeom),
 			(PrevGeom \= Geom ->
-				global_key_newvalue(monitor_geom, Output, Geom),
-				format(string(Msg), "Monitor \"~s\" geometry reconfigured", [Output]),
-				writeln(Msg)
+				(nb_getval(monitor_geom, AMonGeom), gen_assoc(OldMon, AMonGeom, Geom) ->
+					% If a previous monitor has this geom, this one became a mirror, unmanage it
+					delete_monitor(Output),
+					format(string(Msg), "Monitor \"~s\" is a mirror to \"~s\", unmanaging it", [Output, OldMon]),
+					writeln(Msg)
+				;
+					global_key_newvalue(monitor_geom, Output, Geom),
+					format(string(Msg), "Monitor \"~s\" geometry reconfigured", [Output]),
+					writeln(Msg)
+				)
 			; true)
 
 		% Add new monitor
@@ -2040,7 +2047,7 @@
 init_monitor(Mon, Geom) :-
 	% A monitor with this geometry is already managed, don't register mirror
 	nb_getval(monitor_geom, AMonGeom), gen_assoc(OldMon, AMonGeom, Geom) ->
-		format(string(Msg), "Monitor \"~s\" has same geometry as \"~s\", ignoring it", [Mon, OldMon]),
+		format(string(Msg), "Monitor \"~s\" is a mirror to \"~s\", ignoring it", [Mon, OldMon]),
 		writeln(Msg)
 	;