diff --git a/C4/Letters.pm b/C4/Letters.pm
index 8308bac8a9..2bc3030afb 100644
--- a/C4/Letters.pm
+++ b/C4/Letters.pm
@@ -1563,10 +1563,12 @@ sub _get_tt_params {
             my $fk = $config->{$table}->{fk};
 
             if ( $is_a_loop ) {
-                unless ( ref( $tables->{$table} ) eq 'ARRAY' ) {
+                my $values = $tables->{$table} || [];
+                unless ( ref( $values ) eq 'ARRAY' ) {
                     croak "ERROR processing table $table. Wrong API call.";
                 }
-                my $objects = $module->search( { $pk => { -in => $tables->{$table} } } );
+                my $key = $pk ? $pk : $fk;
+                my $objects = $module->search( { $key => { -in => $values } } );
                 $params->{ $config->{$table}->{plural} } = $objects;
             }
             elsif ( $ref eq q{} || $ref eq 'HASH' ) {
diff --git a/t/db_dependent/Letters/TemplateToolkit.t b/t/db_dependent/Letters/TemplateToolkit.t
index cbcfe387c2..e1ee9f821c 100644
--- a/t/db_dependent/Letters/TemplateToolkit.t
+++ b/t/db_dependent/Letters/TemplateToolkit.t
@@ -380,7 +380,7 @@ subtest 'regression tests' => sub {
 };
 
 subtest 'loops' => sub {
-    plan tests => 1;
+    plan tests => 2;
     my $code = "TEST";
     my $module = "TEST";
 
@@ -395,6 +395,20 @@ subtest 'loops' => sub {
         my $expected_letter = join '', ( $patron_1->{surname}, $patron_2->{surname} );
         is( $letter->{content}, $expected_letter, );
     };
+
+    subtest 'foreign key is used' => sub {
+        plan tests => 1;
+        my $patron_1 = $builder->build({ source => 'Borrower' });
+        my $patron_2 = $builder->build({ source => 'Borrower' });
+        my $checkout_1 = $builder->build({ source => 'Issue', value => { borrowernumber => $patron_1->{borrowernumber} } } );
+        my $checkout_2 = $builder->build({ source => 'Issue', value => { borrowernumber => $patron_1->{borrowernumber} } } );
+
+        my $template = q|[% FOREACH checkout IN checkouts %][% checkout.issue_id %][% END %]|;
+        reset_template( { template => $template, code => $code, module => $module } );
+        my $letter = GetPreparedLetter( module => $module, letter_code => $code, loops => { issues => [ $checkout_1->{itemnumber}, $checkout_2->{itemnumber} ] } );
+        my $expected_letter = join '', ( $checkout_1->{issue_id}, $checkout_2->{issue_id} );
+        is( $letter->{content}, $expected_letter, );
+    };
 };
 
 sub reset_template {