diff --git a/Supporters/lib/Supporters.pm b/Supporters/lib/Supporters.pm
index 5e2822a..5d3b545 100644
--- a/Supporters/lib/Supporters.pm
+++ b/Supporters/lib/Supporters.pm
@@ -43,6 +43,12 @@ sub dbh ($) {
 sub ledgerCmd ($) {
   return $_[0]->{ledgerCmd};
 }
+######################################################################
+sub addSupporter ($) {
+  my($sp) = @_;
+
+  die "ledger_entity_id required" unless defined $sp->{ledger_entity_id};
+}
 
 
 1;
diff --git a/Supporters/t/Supporters.t b/Supporters/t/Supporters.t
index 0414d69..c6951db 100644
--- a/Supporters/t/Supporters.t
+++ b/Supporters/t/Supporters.t
@@ -6,7 +6,9 @@
 use strict;
 use warnings;
 
-use Test::More tests => 3;
+use Test::More tests => 4;
+use Test::Exception;
+
 BEGIN { use_ok('Supporters') };
 
 =pod
@@ -24,5 +26,14 @@ my $sp = new Supporters($dbh, "testcmd");
 is($dbh, $sp->dbh());
 is("testcmd", $sp->ledgerCmd());
 
+
+=pod
+
+Test adding a supporter to the database.
+
+=cut
+
+dies_ok { $sp->addSupporter({}) } "ledger_entity_id required";
+
 $dbh->disconnect();