diff --git a/deploy/payment.sql b/deploy/payment.sql
index adb560a..8928df7 100644
--- a/deploy/payment.sql
+++ b/deploy/payment.sql
@@ -19,7 +19,7 @@ create table payment (
 	description text not null,
 	payment_date date not null default current_date,
 	payment_account_id integer not null references payment_account,
-	amount integer not null,
+	amount integer not null constraint payment_amount_positive check (amount > 0),
 	currency_code text not null references currency,
 	tags tag_name[] not null default '{}',
 	payment_status text not null default 'complete' references payment_status,
diff --git a/test/payment.sql b/test/payment.sql
index c471d2a..dac7be5 100644
--- a/test/payment.sql
+++ b/test/payment.sql
@@ -5,7 +5,7 @@ reset client_min_messages;
 
 begin;
 
-select plan(68);
+select plan(71);
 
 set search_path to numerus, auth, public;
 
@@ -17,6 +17,7 @@ select table_privs_are('payment', 'admin', array ['SELECT', 'INSERT', 'UPDATE',
 select table_privs_are('payment', 'authenticator', array []::text[]);
 
 select has_column('payment', 'payment_id');
+select col_is_pk('payment', 'payment_id');
 select col_type_is('payment', 'payment_id', 'integer');
 select col_not_null('payment', 'payment_id');
 select col_hasnt_default('payment', 'payment_id');
@@ -165,6 +166,18 @@ select throws_ok(
 );
 reset role;
 
+select throws_ok(
+	$$ insert into payment (company_id, description, payment_account_id, amount, currency_code) values (2, 'Nope', 221, 0, 'EUR') $$,
+	'23514', 'new row for relation "payment" violates check constraint "payment_amount_positive"',
+	'Should not allow empty payments'
+);
+
+select throws_ok(
+	$$ insert into payment (company_id, description, payment_account_id, amount, currency_code) values (2, 'Nope', 221, -1, 'EUR') $$,
+	'23514', 'new row for relation "payment" violates check constraint "payment_amount_positive"',
+	'Should not allow negative payments'
+);
+
 
 select *
 from finish();