diff --git a/C4/Members.pm b/C4/Members.pm
index c52f18add8..8745b4395a 100644
--- a/C4/Members.pm
+++ b/C4/Members.pm
@@ -635,7 +635,11 @@ sub DeleteExpiredOpacRegistrations {
     my $delay = C4::Context->preference('PatronSelfRegistrationExpireTemporaryAccountsDelay');
     my $category_code = C4::Context->preference('PatronSelfRegistrationDefaultCategory');
 
-    return 0 if not $category_code or not defined $delay or $delay eq q||;
+    return 0 unless $category_code && $delay;
+        # DO NOT REMOVE test on delay here!
+        # Some libraries may not use a temporary category, but want to keep patrons.
+        # We should not delete patrons when the value is NULL, empty string or 0.
+
     my $date_enrolled = dt_from_string();
     $date_enrolled->subtract( days => $delay );
 
diff --git a/koha-tmpl/intranet-tmpl/prog/en/modules/admin/preferences/opac.pref b/koha-tmpl/intranet-tmpl/prog/en/modules/admin/preferences/opac.pref
index 6f618592eb..02a44f1c3c 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/modules/admin/preferences/opac.pref
+++ b/koha-tmpl/intranet-tmpl/prog/en/modules/admin/preferences/opac.pref
@@ -820,13 +820,14 @@ OPAC:
             - pref: PatronSelfRegistrationDefaultCategory
               choices: patron-categories
             - "as the default patron category for patrons registered via the OPAC."
-            - "<br><strong>WARNING: Do not use a regular patron category for self registration.</strong> If the <code>misc/cronjobs/cleanup_database.pl</code> cronjob is setup to delete unverified and unfinished OPAC self registrations, it will permanently and unrecoverably delete all patrons that have registered more than <a href='/cgi-bin/koha/admin/preferences.pl?op=search&searchfield=PatronSelfRegistrationExpireTemporaryAccountsDelay'>PatronSelfRegistrationExpireTemporaryAccountsDelay</a> days ago."
+            - "<br><strong>WARNING: Do not use a regular patron category for self registration.</strong><br>
+If the <code>misc/cronjobs/cleanup_database.pl</code> cronjob is setup to delete unverified and unfinished OPAC self registrations, it will permanently and unrecoverably delete all patrons that have registered more than <a href='/cgi-bin/koha/admin/preferences.pl?op=search&searchfield=PatronSelfRegistrationExpireTemporaryAccountsDelay'>PatronSelfRegistrationExpireTemporaryAccountsDelay</a> days ago (unless that delay is empty or zero)."
         -
             - Delete patrons still in the category indicated by <a href="/cgi-bin/koha/admin/preferences.pl?op=search&searchfield=PatronSelfRegistrationDefaultCategory">PatronSelfRegistrationDefaultCategory</a>
             - pref: PatronSelfRegistrationExpireTemporaryAccountsDelay
               class: integer
             - "days after account creation."
-            - "<br><strong>NOTE:</strong> This system preference requires the <code>misc/cronjobs/cleanup_database.pl</code> cronjob. Ask your system administrator to schedule it."
+            - "<br><strong>NOTE:</strong> This system preference requires the <code>misc/cronjobs/cleanup_database.pl</code> cronjob. Ask your system administrator to schedule it.<br>No patrons will be deleted if you set the pref to zero or make it empty."
         -
             - "The following <a href='http://schema.koha-community.org/__VERSION__/tables/borrowers.html' target='blank'>database columns</a> must be filled in on the patron entry screen:"
             - pref: PatronSelfRegistrationBorrowerMandatoryField
diff --git a/t/db_dependent/Members.t b/t/db_dependent/Members.t
index 367d0d2aff..b689cbe1c7 100755
--- a/t/db_dependent/Members.t
+++ b/t/db_dependent/Members.t
@@ -403,7 +403,7 @@ $borrower = Koha::Patrons->find( $borrowernumber )->unblessed;
 ok( $borrower->{userid},  'A userid should have been generated correctly' );
 
 subtest 'purgeSelfRegistration' => sub {
-    plan tests => 5;
+    plan tests => 8;
 
     #purge unverified
     my $d=360;
@@ -417,7 +417,6 @@ subtest 'purgeSelfRegistration' => sub {
     my $c= 'XYZ';
     $dbh->do("INSERT IGNORE INTO categories (categorycode) VALUES ('$c')");
     t::lib::Mocks::mock_preference('PatronSelfRegistrationDefaultCategory', $c );
-    t::lib::Mocks::mock_preference('PatronSelfRegistrationExpireTemporaryAccountsDelay', 360);
     C4::Members::DeleteExpiredOpacRegistrations();
     my $self_reg = $builder->build_object({
         class => 'Koha::Patrons',
@@ -427,6 +426,18 @@ subtest 'purgeSelfRegistration' => sub {
         }
     });
 
+    # First test if empty PatronSelfRegistrationExpireTemporaryAccountsDelay returns zero
+    t::lib::Mocks::mock_preference('PatronSelfRegistrationExpireTemporaryAccountsDelay', q{} );
+    is( C4::Members::DeleteExpiredOpacRegistrations(), 0, "DeleteExpiredOpacRegistrations with empty delay" );
+    # Test zero too
+    t::lib::Mocks::mock_preference('PatronSelfRegistrationExpireTemporaryAccountsDelay', 0 );
+    is( C4::Members::DeleteExpiredOpacRegistrations(), 0, "DeleteExpiredOpacRegistrations with delay 0" );
+    # Also check empty category
+    t::lib::Mocks::mock_preference('PatronSelfRegistrationDefaultCategory', q{} );
+    t::lib::Mocks::mock_preference('PatronSelfRegistrationExpireTemporaryAccountsDelay', 360 );
+    is( C4::Members::DeleteExpiredOpacRegistrations(), 0, "DeleteExpiredOpacRegistrations with empty category" );
+    t::lib::Mocks::mock_preference('PatronSelfRegistrationDefaultCategory', $c );
+
     my $checkout     = $builder->build_object({
         class=>'Koha::Checkouts',
         value=>{