diff --git a/res/schema.sql b/res/schema.sql
index 8ce1756b9..29d2c2baf 100644
--- a/res/schema.sql
+++ b/res/schema.sql
@@ -4,6 +4,7 @@ CREATE TABLE IF NOT EXISTS keys(
     key_public BLOB NOT NULL,
     key_private BLOB NOT NULL
 );
+PRAGMA foreign_keys=on;
 CREATE TABLE IF NOT EXISTS coins(
     coin_id INTEGER PRIMARY KEY NOT NULL,
     coin BLOB NOT NULL,
@@ -11,7 +12,10 @@ CREATE TABLE IF NOT EXISTS coins(
     serial BLOB NOT NULL,
     value INT NOT NULL,
     coin_blind BLOB NOT NULL,
-    valcom_blind BLOB NOT NULL
+    valcom_blind BLOB NOT NULL,
+    key_id INTEGER NOT NULL,
+    FOREIGN KEY (key_id)
+        REFERENCES keys (key_id)
 );
 CREATE TABLE IF NOT EXISTS cashier(
     key_id INTEGER PRIMARY KEY NOT NULL,