diff --git a/fhem/FHEM/14_CUL_MAX.pm b/fhem/FHEM/14_CUL_MAX.pm
index 138707822..c50e182b4 100644
--- a/fhem/FHEM/14_CUL_MAX.pm
+++ b/fhem/FHEM/14_CUL_MAX.pm
@@ -69,7 +69,11 @@ CUL_MAX_Define($$)
   $hash->{retryCount} = 0;
   $hash->{devices} = ();
   AssignIoPort($hash);
-  CUL_MAX_Check($hash);
+
+  if(CUL_MAX_Check($hash)) {
+    #Doing this on older firmware disables MAX mode
+    IOWrite($hash, "", "Za". $hash->{addr});
+  }
 
   #This interface is shared with 00_MAXLAN.pm
   $hash->{SendDeviceCmd} = \&CUL_MAX_SendDeviceCmd;
@@ -109,9 +113,11 @@ CUL_MAX_Check($@)
   #Looks like "V 1.49 CUL868"
   $version =~ m/V (.*)\.(.*) CUL.*/;
   my ($major_version,$minorversion) = ($1, $2);
-  if($major_version == 1 and $minorversion < 50) {
-    Log 2, "The current firmware of the CUL has known bugs with respect to MAX! support. Please update."
+  if($major_version == 1 and $minorversion < 52) {
+    Log 2, "The current firmware of the CUL has known bugs with respect to MAX! support. Please update.";
+    return 0;
   }
+  return 1;
 }
 
 sub
@@ -170,6 +176,7 @@ CUL_MAX_Parse($$)
   if(exists($msgId2Cmd{$msgTypeRaw})) {
 
     if($msgType eq "Ack") {
+      return undef if($src eq $shash->{addr}); #Ignore packets generated by culfw's auto-Ack
       Dispatch($shash, "MAX,$isToMe,Ack,$src,$payload", {RAWMSG => $rmsg});
 
       return undef if(!$isToMe);