diff --git a/README.md b/README.md
index 0fd52d2..748d885 100644
--- a/README.md
+++ b/README.md
@@ -360,6 +360,10 @@ bank_account = client.bank_accounts.find('1')
 ```ruby
 bank_account.deactivate
 ```
+Optionally a *mobile_pin* can be passed as argument.
+```ruby
+bank_account.deactivate('mobile_pin')
+```
 #####Get a bank account's users
 ```ruby
 bank_account.user
diff --git a/lib/promisepay/models/bank_account.rb b/lib/promisepay/models/bank_account.rb
index 81cc10a..bc436db 100644
--- a/lib/promisepay/models/bank_account.rb
+++ b/lib/promisepay/models/bank_account.rb
@@ -19,7 +19,7 @@ def user
     # @param mobile_pin [String] Mobile PIN.
     #
     # @return [Boolean]
-    def deactivate(mobile_pin)
+    def deactivate(mobile_pin = nil)
       @client.delete("bank_accounts/#{id}", mobile_pin: mobile_pin)
       @attributes['active'] = false
       true
diff --git a/spec/fixtures/bank_accounts_deactivated_no_pin.yml b/spec/fixtures/bank_accounts_deactivated_no_pin.yml
new file mode 100644
index 0000000..b865b02
--- /dev/null
+++ b/spec/fixtures/bank_accounts_deactivated_no_pin.yml
@@ -0,0 +1,66 @@
+---
+http_interactions:
+- request:
+    method: delete
+    uri: https://<USERNAME>:<TOKEN>@test.api.promisepay.com/bank_accounts/a4355e4c-25e4-49e3-88bf-63de71bbbea9
+    body:
+      encoding: UTF-8
+      string: '{"mobile_pin":null}'
+    headers:
+      User-Agent:
+      - Faraday v0.11.0
+      Content-Type:
+      - application/json
+      Accept-Encoding:
+      - gzip;q=1.0,deflate;q=0.6,identity;q=0.3
+      Accept:
+      - "*/*"
+  response:
+    status:
+      code: 200
+      message: OK
+    headers:
+      Date:
+      - Thu, 19 Jan 2017 04:44:21 GMT
+      Content-Type:
+      - application/json; charset=utf-8
+      Transfer-Encoding:
+      - chunked
+      Connection:
+      - keep-alive
+      Access-Control-Allow-Headers:
+      - Origin, Content-Type, Accept, Authorization, Token
+      Access-Control-Allow-Methods:
+      - POST, GET, PUT, DELETE, OPTIONS
+      Access-Control-Allow-Origin:
+      - "*"
+      Access-Control-Max-Age:
+      - '1728000'
+      Access-Control-Request-Method:
+      - "*"
+      Cache-Control:
+      - max-age=0, private, must-revalidate
+      Etag:
+      - W/"652727d4dd734c741f93f8884be7f597"
+      Server:
+      - nginx/1.8.0 + Phusion Passenger 4.0.59
+      Status:
+      - 200 OK
+      X-Content-Type-Options:
+      - nosniff
+      X-Frame-Options:
+      - SAMEORIGIN
+      X-Powered-By:
+      - Phusion Passenger 4.0.59
+      X-Request-Id:
+      - 3dc30844-c5f4-4f31-8d70-a84fb3224676
+      X-Runtime:
+      - '0.244601'
+      X-Xss-Protection:
+      - 1; mode=block
+    body:
+      encoding: ASCII-8BIT
+      string: '{"bank_account":"Successfully redacted"}'
+    http_version:
+  recorded_at: Thu, 19 Jan 2017 04:44:22 GMT
+recorded_with: VCR 3.0.3
diff --git a/spec/fixtures/bank_accounts_single_2.yml b/spec/fixtures/bank_accounts_single_2.yml
new file mode 100644
index 0000000..3bb79b2
--- /dev/null
+++ b/spec/fixtures/bank_accounts_single_2.yml
@@ -0,0 +1,65 @@
+---
+http_interactions:
+- request:
+    method: get
+    uri: https://<USERNAME>:<TOKEN>@test.api.promisepay.com/bank_accounts/a4355e4c-25e4-49e3-88bf-63de71bbbea9
+    body:
+      encoding: US-ASCII
+      string: ''
+    headers:
+      User-Agent:
+      - Faraday v0.11.0
+      Accept-Encoding:
+      - gzip;q=1.0,deflate;q=0.6,identity;q=0.3
+      Accept:
+      - "*/*"
+  response:
+    status:
+      code: 200
+      message: OK
+    headers:
+      Date:
+      - Thu, 19 Jan 2017 04:44:20 GMT
+      Content-Type:
+      - application/json; charset=utf-8
+      Transfer-Encoding:
+      - chunked
+      Connection:
+      - keep-alive
+      Access-Control-Allow-Headers:
+      - Origin, Content-Type, Accept, Authorization, Token
+      Access-Control-Allow-Methods:
+      - POST, GET, PUT, DELETE, OPTIONS
+      Access-Control-Allow-Origin:
+      - "*"
+      Access-Control-Max-Age:
+      - '1728000'
+      Access-Control-Request-Method:
+      - "*"
+      Cache-Control:
+      - max-age=0, private, must-revalidate
+      Etag:
+      - W/"09c612afc7b10f01b4b41275ff7bf85d"
+      Server:
+      - nginx/1.8.0 + Phusion Passenger 4.0.59
+      Status:
+      - 200 OK
+      X-Content-Type-Options:
+      - nosniff
+      X-Frame-Options:
+      - SAMEORIGIN
+      X-Powered-By:
+      - Phusion Passenger 4.0.59
+      X-Request-Id:
+      - fea6add5-977c-4af2-9bca-02bfe89ed25b
+      X-Runtime:
+      - '0.268324'
+      X-Xss-Protection:
+      - 1; mode=block
+    body:
+      encoding: ASCII-8BIT
+      string: '{"bank_accounts":{"id":"a4355e4c-25e4-49e3-88bf-63de71bbbea9","active":true,"created_at":"2017-01-19T04:41:01.747Z","updated_at":"2017-01-19T04:41:01.747Z","verification_status":"not_verified","currency":"AUD","bank":{"bank_name":"Bank
+        test","country":"AUS","account_name":"Mr x","routing_number":"XXXXX3","account_number":"XXX345","holder_type":"personal","account_type":"savings","direct_debit_authority_status":null},"links":{"self":"/bank_accounts/a4355e4c-25e4-49e3-88bf-63de71bbbea9","users":"/bank_accounts/a4355e4c-25e4-49e3-88bf-63de71bbbea9/users","direct_debit_authorities":"/bank_accounts/a4355e4c-25e4-49e3-88bf-63de71bbbea9/direct_debit_authorities"}}}'
+    http_version:
+  recorded_at: Thu, 19 Jan 2017 04:44:20 GMT
+recorded_with: VCR 3.0.3
diff --git a/spec/promisepay/models/bank_account_spec.rb b/spec/promisepay/models/bank_account_spec.rb
index e812411..9f368f2 100644
--- a/spec/promisepay/models/bank_account_spec.rb
+++ b/spec/promisepay/models/bank_account_spec.rb
@@ -8,6 +8,12 @@
     end
   end
 
+  let(:account2) do
+    VCR.use_cassette('bank_accounts_single_2') do
+      client.bank_accounts.find('a4355e4c-25e4-49e3-88bf-63de71bbbea9')
+    end
+  end
+
   describe 'user', vcr: { cassette_name: 'bank_accounts_user' } do
     it 'gives back the account owner' do
       expect(account.user).to be_a(Promisepay::User)
@@ -15,10 +21,15 @@
   end
 
   describe 'deactivate' do
-    it 'deactivates the account', vcr: { cassette_name: 'bank_accounts_deactivated' } do
+    it 'with mobile-pin', vcr: { cassette_name: 'bank_accounts_deactivated' } do
       expect(account.active).to be(true)
       account.deactivate('123')
       expect(account.active).to be(false)
     end
+    it 'without mobile-pin', vcr: { cassette_name: 'bank_accounts_deactivated_no_pin'} do
+      expect(account2.active).to be(true)
+      account2.deactivate()
+      expect(account2.active).to be(false)
+    end
   end
 end