diff --git a/lib/mangopay.rb b/lib/mangopay.rb
index 7a1bf1e..f29a627 100644
--- a/lib/mangopay.rb
+++ b/lib/mangopay.rb
@@ -214,7 +214,13 @@ def request(method, url, params={}, filters={}, headers_or_idempotency_key = nil
       raise MangoPay::ResponseError.new(uri, '408', {'Message' => 'Request Timeout'}) if res.nil?
 
       # decode json data
-      data = res.body.to_s.empty? ? {} : JSON.load(res.body.to_s)
+      begin
+        data = res.body.to_s.empty? ? {} : JSON.load(res.body.to_s)
+      rescue MultiJson::ParseError
+        details = {}
+        details['Message'] = res.body
+        raise MangoPay::ResponseError.new(uri, res.code, details)
+      end
 
       unless res.is_a?(Net::HTTPOK)
         raise MangoPay::ResponseError.new(uri, res.code, data)
@@ -298,12 +304,17 @@ def do_request_with_log(http, req, uri)
         res
       ensure
         line = "#{log_severity(res)} #{line}"
+        if time.nil?
+          time_log = "[Unknown ms]"
+        else
+          time_log = "[#{(time * 1000).round(1)}ms]"
+        end
         if res.nil?
           params = ''
-          line += "\n  [#{(time * 1000).round(1)}ms] 408 Request Timeout #{params}\n"
+          line += "\n  #{time_log} 408 Request Timeout #{params}\n"
         else
           params = FilterParameters.response(res.body)
-          line += "\n  [#{(time * 1000).round(1)}ms] #{res.code} #{params}\n"
+          line += "\n  #{time_log} #{res.code} #{params}\n"
         end
         logger.info { line }
       end
diff --git a/spec/mangopay/card_registration_spec.rb b/spec/mangopay/card_registration_spec.rb
index 3c030fe..16a4bae 100644
--- a/spec/mangopay/card_registration_spec.rb
+++ b/spec/mangopay/card_registration_spec.rb
@@ -6,7 +6,6 @@
     it 'creates a new card registration' do
       created = new_card_registration
       expect(created['Id']).not_to be_nil
-      expect(created['Id'].to_i).to be > 0
       expect(created['AccessKey']).not_to be_nil
       expect(created['PreregistrationData']).not_to be_nil
       expect(created['CardRegistrationURL']).not_to be_nil
@@ -51,7 +50,6 @@
 
       # card id filled-in...
       expect(card_id).not_to be_nil
-      expect(card_id.to_i).to be > 0
 
       # ...and points to existing (newly created) card
       card = MangoPay::Card.fetch(card_id)
diff --git a/spec/mangopay/preauthorization_spec.rb b/spec/mangopay/preauthorization_spec.rb
index 277dd8f..3f7fe71 100644
--- a/spec/mangopay/preauthorization_spec.rb
+++ b/spec/mangopay/preauthorization_spec.rb
@@ -7,7 +7,6 @@
       cardreg = new_card_registration_completed
       created = new_card_preauthorization
       expect(created['Id']).not_to be_nil
-      expect(created['Id'].to_i).to be > 0
       expect(created['CardId']).to eq(cardreg['CardId'])
       expect(created['AuthorId']).to eq(new_natural_user["Id"])
       expect(created['PayInId']).to be_nil
diff --git a/spec/mangopay/user_spec.rb b/spec/mangopay/user_spec.rb
index b42c089..083c15a 100644
--- a/spec/mangopay/user_spec.rb
+++ b/spec/mangopay/user_spec.rb
@@ -144,7 +144,6 @@
         fetched = MangoPay::Card.fetch(card['CardId'])
 
         expect(fetched['Id']).not_to be_nil
-        expect(fetched['Id'].to_i).to be > 0
         expect(fetched['UserId']).to eq(new_natural_user["Id"])
         expect(fetched['Currency']).to eq('EUR')
       end