diff --git a/app/models/user_device.rb b/app/models/user_device.rb
index 15d7b3698..444703d15 100644
--- a/app/models/user_device.rb
+++ b/app/models/user_device.rb
@@ -21,8 +21,9 @@ store new device for user if device not already known
 
   def self.add(user_agent, ip, user_id, fingerprint, type)
 
-    # since gem browser 2 is not handling nil for user_agent, set it to ''
-    user_agent ||= ''
+    if user_agent.blank?
+      user_agent = 'unknown'
+    end
 
     # get location info
     location_details = Service::GeoIp.location(ip)
@@ -60,23 +61,26 @@ store new device for user if device not already known
     end
 
     # get browser details
-    browser = Browser.new(user_agent, accept_language: 'en-us')
-    browser = {
-      plattform: browser.platform.to_s.camelize,
-      name: browser.name,
-      version: browser.version,
-      full_version: browser.full_version,
-    }
+    browser = {}
+    if user_agent != 'unknown'
+      browser = Browser.new(user_agent, accept_language: 'en-us')
+      browser = {
+        plattform: browser.platform.to_s.camelize,
+        name: browser.name,
+        version: browser.version,
+        full_version: browser.full_version,
+      }
+    end
 
     # generate device name
     if browser[:name] == 'Generic Browser'
       browser[:name] = user_agent
     end
     name = ''
-    if browser[:plattform] && browser[:plattform] != 'Other'
+    if browser[:plattform].present? && browser[:plattform] != 'Other'
       name = browser[:plattform]
     end
-    if browser[:name] && browser[:name] != 'Other'
+    if browser[:name].present? && browser[:name] != 'Other'
       if name.present?
         name += ', '
       end
@@ -84,7 +88,7 @@ store new device for user if device not already known
     end
 
     # if not identified, use user agent
-    if !name || name == '' || name == 'Other, Other' || name == 'Other'
+    if name.blank? || name == 'Other, Other' || name == 'Other'
       name = user_agent
       browser[:name] = user_agent
     end
@@ -103,7 +107,7 @@ store new device for user if device not already known
     end
 
     # create new device
-    user_device = create(
+    user_device = create!(
       user_id: user_id,
       name: name,
       os: browser[:plattform],
diff --git a/test/unit/user_device_test.rb b/test/unit/user_device_test.rb
index cd734e971..4d1ff1e52 100644
--- a/test/unit/user_device_test.rb
+++ b/test/unit/user_device_test.rb
@@ -204,6 +204,42 @@ class UserDeviceTest < ActiveSupport::TestCase
     )
     assert_equal(user_device2.id, user_device6.id)
 
+    # signin without ua from country A via basic auth -> new device #3
+    user_device7 = UserDevice.add(
+      '',
+      '91.115.248.231',
+      @agent.id,
+      nil,
+      'basic_auth',
+    )
+    assert_not_equal(user_device6.id, user_device7.id)
+
+    user_device8 = UserDevice.add(
+      '',
+      '91.115.248.231',
+      @agent.id,
+      nil,
+      'basic_auth',
+    )
+    assert_equal(user_device7.id, user_device8.id)
+
+    user_device9 = UserDevice.add(
+      nil,
+      '91.115.248.231',
+      @agent.id,
+      nil,
+      'basic_auth',
+    )
+    assert_equal(user_device8.id, user_device9.id)
+
+    user_device10 = UserDevice.add(
+      nil,
+      '176.198.137.254',
+      @agent.id,
+      nil,
+      'basic_auth',
+    )
+    assert_not_equal(user_device9.id, user_device10.id)
   end
 
   test 'ddd - api test' do