diff --git a/Kernel/Modules/AdminCustomerCompany.pm b/Kernel/Modules/AdminCustomerCompany.pm
index 0b1eabb2f6..bce744999c 100644
--- a/Kernel/Modules/AdminCustomerCompany.pm
+++ b/Kernel/Modules/AdminCustomerCompany.pm
@@ -19,12 +19,17 @@ package Kernel::Modules::AdminCustomerCompany;
 use strict;
 use warnings;
 
-use Kernel::Language qw(Translatable);
+# core modules
+use List::Util qw(any);
 
-our $ObjectManagerDisabled = 1;
+# CPAN modules
 
+# OTOBO modules
+use Kernel::Language qw(Translatable);
 use Kernel::System::VariableCheck qw(:all);
 
+our $ObjectManagerDisabled = 1;
+
 sub new {
     my ( $Type, %Param ) = @_;
 
@@ -99,11 +104,23 @@ sub Run {
         my %Errors;
         $GetParam{CustomerCompanyID} = $ParamObject->GetParam( Param => 'CustomerCompanyID' );
 
+        my @CustomerCompanyMap = $ConfigObject->Get( $GetParam{Source} )->{Map}->@*;
+
+        # The readonly fields should not be settable from the WebApp.
+        # So update with the old values, regardless what was passed from the client.
+        # The old data is only needed when there are any readonly fields.
+        my %OldData;
+        if ( any { $_->[7] } @CustomerCompanyMap ) {
+            %OldData = $CustomerCompanyObject->CustomerCompanyGet(
+                CustomerID => $GetParam{CustomerCompanyID},
+            );
+        }
+
         # Get dynamic field backend object.
         my $DynamicFieldBackendObject = $Kernel::OM->Get('Kernel::System::DynamicField::Backend');
 
         ENTRY:
-        for my $Entry ( @{ $ConfigObject->Get( $GetParam{Source} )->{Map} } ) {
+        for my $Entry ( @CustomerCompanyMap ) {
 
             # check dynamic fields
             if ( $Entry->[5] eq 'dynamic_field' ) {
@@ -138,6 +155,11 @@ sub Run {
                 }
             }
 
+            # reuse the old data for readonly field
+            elsif ( $Entry->[7] ) {
+                $GetParam{ $Entry->[0] } = $OldData{ $Entry->[0] };
+            }
+
             # check remaining non-dynamic-field mandatory fields
             else {
                 $GetParam{ $Entry->[0] } = $ParamObject->GetParam( Param => $Entry->[0] ) // '';
@@ -180,7 +202,7 @@ sub Run {
                 my $DynamicFieldObject = $Kernel::OM->Get('Kernel::System::DynamicField');
 
                 ENTRY:
-                for my $Entry ( @{ $ConfigObject->Get( $GetParam{Source} )->{Map} } ) {
+                for my $Entry ( @CustomerCompanyMap ) {
                     next ENTRY if $Entry->[5] ne 'dynamic_field';
 
                     my $DynamicFieldConfig = $Self->{DynamicFieldLookup}->{ $Entry->[2] };
diff --git a/Kernel/System/CustomerCompany/DB.pm b/Kernel/System/CustomerCompany/DB.pm
index 6386fe9bc8..4cedfd8b03 100644
--- a/Kernel/System/CustomerCompany/DB.pm
+++ b/Kernel/System/CustomerCompany/DB.pm
@@ -910,28 +910,27 @@ sub CustomerCompanyUpdate {
     }
 
     # check needed stuff
+    FIELD:
     for my $Entry ( @{ $Self->{CustomerCompanyMap}->{Map} } ) {
-        if (
-            !$Param{ $Entry->[0] }
-            && $Entry->[5] ne 'dynamic_field'    # ignore dynamic fields here
-            && $Entry->[4]
-            && $Entry->[0] ne 'UserPassword'
-            )
-        {
-            $Kernel::OM->Get('Kernel::System::Log')->Log(
-                Priority => 'error',
-                Message  => "Need $Entry->[0]!"
-            );
-            return;
-        }
-    }
+        next FIELD if $Param{ $Entry->[0] };            # worry only about empty fields, '0' is considered as being empty
+        next FIELD if $Entry->[5] eq 'dynamic_field';   # do not complain about missing dynamic fields
+        next FIELD if !$Entry->[4];                     # complain only about missing required fields
+        next FIELD if $Entry->[0] eq 'UserPassword';    # do not complain about missing password field
 
-    my @Fields;
-    my @Values;
+        $Kernel::OM->Get('Kernel::System::Log')->Log(
+            Priority => 'error',
+            Message  => "Need $Entry->[0]!"
+        );
+
+        return;
+    }
 
+    # Collect the info needed for the SQL UPDATE statement
+    # The readonly flag is not honored here.
+    my ( @Fields, @Values );
     FIELD:
     for my $Entry ( @{ $Self->{CustomerCompanyMap}->{Map} } ) {
-        next FIELD if $Entry->[0] =~ /^UserPassword$/i;
+        next FIELD if $Entry->[0] =~ m/^UserPassword$/i;  # skip the password field
         next FIELD if $Entry->[5] eq 'dynamic_field';     # skip dynamic fields
         push @Fields, $Entry->[2] . ' = ?';
         push @Values, \$Param{ $Entry->[0] };