diff --git a/FHEM/32_SYSSTAT.pm b/FHEM/32_SYSSTAT.pm
index 1fedce218..c6dc9b1ab 100644
--- a/FHEM/32_SYSSTAT.pm
+++ b/FHEM/32_SYSSTAT.pm
@@ -459,7 +459,7 @@ SYSSTAT_readOIDs($$)
 
     my @snmpoids = ();
     my @nextid   = keys %$response;
-    while ( $nextid[0] =~ m/^$snmpoids/ ) {
+    while ( $snmpoids && $nextid[0] =~ m/^$snmpoids/ ) {
       push( @snmpoids, $nextid[0] );
 
       $response = $hash->{session}->get_next_request( $nextid[0] );
diff --git a/FHEM/32_mailcheck.pm b/FHEM/32_mailcheck.pm
index bf77db862..d1798edcb 100755
--- a/FHEM/32_mailcheck.pm
+++ b/FHEM/32_mailcheck.pm
@@ -120,6 +120,8 @@ mailcheck_Notify($$)
   return if(!grep(m/^INITIALIZED|REREADCFG$/, @{$dev->{CHANGED}}));
 
   mailcheck_Connect($hash);
+
+  return undef;
 }
 
 sub
diff --git a/FHEM/32_withings.pm b/FHEM/32_withings.pm
index 3e144e592..12b84fd30 100644
--- a/FHEM/32_withings.pm
+++ b/FHEM/32_withings.pm
@@ -137,6 +137,8 @@ withings_Notify($$)
   withings_initUser($hash) if( $hash->{SUBTYPE} eq "USER" );
   withings_connect($hash) if( $hash->{SUBTYPE} eq "ACCOUNT" );
   withings_initDevice($hash) if( $hash->{SUBTYPE} eq "DEVICE" );
+
+  return undef;
 }
 
 sub
diff --git a/FHEM/37_harmony.pm b/FHEM/37_harmony.pm
index 621489587..1868e26af 100644
--- a/FHEM/37_harmony.pm
+++ b/FHEM/37_harmony.pm
@@ -108,6 +108,8 @@ harmony_Notify($$)
   return if(!grep(m/^INITIALIZED|REREADCFG$/, @{$dev->{CHANGED}}));
 
   harmony_connect($hash) if( !defined($hash->{id}) );
+
+  return undef;
 }
 
 sub
diff --git a/FHEM/38_netatmo.pm b/FHEM/38_netatmo.pm
index 1066999d9..80626042b 100644
--- a/FHEM/38_netatmo.pm
+++ b/FHEM/38_netatmo.pm
@@ -190,6 +190,8 @@ netatmo_Notify($$)
   netatmo_connect($hash) if( $hash->{SUBTYPE} eq "ACCOUNT" );
   netatmo_initDevice($hash) if( $hash->{SUBTYPE} eq "DEVICE" );
   netatmo_initDevice($hash) if( $hash->{SUBTYPE} eq "MODULE" );
+
+  return undef;
 }
 
 sub