diff --git a/fhem/FHEM/10_MAX.pm b/fhem/FHEM/10_MAX.pm
index 2503396b0..3238fffeb 100755
--- a/fhem/FHEM/10_MAX.pm
+++ b/fhem/FHEM/10_MAX.pm
@@ -8,6 +8,7 @@ use warnings;
 use MIME::Base64;
 
 sub MAX_Define($$);
+sub MAX_Undef($$);
 sub MAX_Initialize($);
 sub MAX_Parse($$);
 sub MAX_Set($@);
@@ -42,6 +43,7 @@ MAX_Initialize($)
   Log 5, "Calling MAX_Initialize";
   $hash->{Match}     = "^MAX";
   $hash->{DefFn}     = "MAX_Define";
+  $hash->{UndefFn}   = "MAX_Undef";
   $hash->{ParseFn}   = "MAX_Parse";
   $hash->{SetFn}     = "MAX_Set";
   $hash->{AttrList}  = "IODev do_not_notify:1,0 ignore:0,1 dummy:0,1 " .
@@ -79,6 +81,13 @@ MAX_Define($$)
   return undef;
 }
 
+sub
+MAX_Undef($$)
+{
+  my ($hash,$name) = @_;
+  delete($modules{MAX}{defptr}{$hash->{addr}});
+}
+
 sub
 MAX_DateTime2Internal($)
 {
diff --git a/fhem/FHEM/14_CUL_MAX.pm b/fhem/FHEM/14_CUL_MAX.pm
index a9c3516cc..2779e7bac 100644
--- a/fhem/FHEM/14_CUL_MAX.pm
+++ b/fhem/FHEM/14_CUL_MAX.pm
@@ -85,6 +85,7 @@ CUL_MAX_Undef($$)
 {
   my ($hash, $name) = @_;
   RemoveInternalTimer($hash);
+  delete($modules{CUL_MAX}{defptr});
   return undef;
 }