diff --git a/integration/ocean/AssetOwners.test.ts b/integration/ocean/AssetOwners.test.ts
index dbdd624..1eea73a 100644
--- a/integration/ocean/AssetOwners.test.ts
+++ b/integration/ocean/AssetOwners.test.ts
@@ -37,6 +37,16 @@ describe('Asset Owners', () => {
         assert.isTrue(isProvider)
     })
 
+    it('should be added correctly a permission on an asset', async () => {
+        const ddo = await ocean.assets.create(metadata as any, account1)
+
+        assert.isFalse(await ocean.keeper.didRegistry.getPermission(ddo.id, account2.getId()))
+
+        await ocean.keeper.didRegistry.grantPermission(ddo.id, account2.getId(), account1.getId())
+
+        assert.isTrue(await ocean.keeper.didRegistry.getPermission(ddo.id, account2.getId()))
+    })
+
     it('should get the assets owned by a user', async () => {
         const { length: initialLength } = await ocean.assets.ownerAssets(account2.getId())
 
diff --git a/src/keeper/contracts/DIDRegistry.ts b/src/keeper/contracts/DIDRegistry.ts
index 90e6883..13f29e1 100644
--- a/src/keeper/contracts/DIDRegistry.ts
+++ b/src/keeper/contracts/DIDRegistry.ts
@@ -50,7 +50,7 @@ export default class DIDRegistry extends ContractBase {
     }
 
     public async grantPermission(did: string, grantee: string, ownerAddress: string) {
-        return this.send('grantPermission', ownerAddress, [zeroX(did), zeroX(grantee)])
+        return this.send('grantPermission', ownerAddress, [didZeroX(did), zeroX(grantee)])
     }
 
     public async revokePermission(did: string, grantee: string, ownerAddress: string) {