diff --git a/Supporters/lib/Supporters.pm b/Supporters/lib/Supporters.pm
index 6229fb0..1786de0 100644
--- a/Supporters/lib/Supporters.pm
+++ b/Supporters/lib/Supporters.pm
@@ -481,7 +481,8 @@ sub _verifyId($$) {
 
   die "_verifyId() called with a non-numeric id" unless defined $id and looks_like_number($id);
 
-  my $val = $self->dbh()->selectall_hashref("SELECT id FROM supporter WHERE id = $id", 'id');
+  my $val = $self->dbh()->selectall_hashref("SELECT id FROM supporter WHERE id = " .
+                                            $self->dbh->quote($id, 'SQL_INTEGER'), 'id');
   return (defined $val and defined $val->{$id});
 
 }