diff --git a/app/helpers/account_helper.rb b/app/helpers/account_helper.rb
index 09ed494..9a6c13d 100644
--- a/app/helpers/account_helper.rb
+++ b/app/helpers/account_helper.rb
@@ -15,12 +15,17 @@ module AccountHelper
 
   def suggestion_based_on_username(requested_username='')
     return "" if requested_username.empty?
+
+    requested_username = requested_username.downcase.tr("^#{Profile::IDENTIFIER_FORMAT}", '')
     usernames = []
+    tries = 0
     3.times do
       begin
         valid_name = requested_username + rand(1000).to_s
-      end while (usernames.include?(valid_name) || !Person.is_available?(valid_name, environment))
-      usernames << valid_name
+        tries += 1
+        invalid = usernames.include?(valid_name) || !Person.is_available?(valid_name, environment)
+      end while tries <= 10 && invalid
+      usernames << valid_name unless invalid
     end
     usernames
   end
diff --git a/test/unit/account_helper_test.rb b/test/unit/account_helper_test.rb
index 69656aa..4f39e83 100644
--- a/test/unit/account_helper_test.rb
+++ b/test/unit/account_helper_test.rb
@@ -18,4 +18,19 @@ class AccountHelperTest < ActiveSupport::TestCase
     end
   end
 
+  should 'remove chars which are not allowed' do
+    stubs(:environment).returns(Environment.default)
+    suggestions = suggestion_based_on_username('z/%&#e')
+    suggestions.each do |suggestion|
+      assert_no_match /.*%&#.*/, suggestion
+    end
+  end
+
+  should 'return empty suggestions if do not find any identifier available' do
+    stubs(:environment).returns(Environment.default)
+    Person.stubs(:is_available?).returns(false)
+    suggestions = suggestion_based_on_username('z/%&#e')
+    assert_equal [], suggestions
+  end
+
 end
--
libgit2 0.21.2