diff --git a/app/models/user.rb b/app/models/user.rb
index bec279eb2..4bb8c6856 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -546,11 +546,17 @@ class User < Principal
   def self.find_by_login(login)
     login = Redmine::CodesetUtil.replace_invalid_utf8(login.to_s)
     if login.present?
+      users = where(:login => login)
       # First look for an exact match
-      user = where(:login => login).detect {|u| u.login == login}
+      user = users.detect {|u| u.login == login}
       unless user
         # Fail over to case-insensitive if none was found
-        user = find_by("LOWER(login) = ?", login.downcase)
+        if Redmine::Database.mysql? || Redmine::Database.sqlserver?
+          # MySQL and SQLServer are case-insensitive by default, we can search in the existing results
+          user = users.detect {|u| u.login.casecmp?(login)}
+        else
+          user = find_by("LOWER(login) = ?", login.downcase)
+        end
       end
       user
     end
diff --git a/lib/redmine/database.rb b/lib/redmine/database.rb
index 13c92b8a4..7c95d5da3 100644
--- a/lib/redmine/database.rb
+++ b/lib/redmine/database.rb
@@ -65,6 +65,10 @@ module Redmine
         mysql? ? ActiveRecord::Base.connection.select_value("SELECT VERSION()") : nil
       end
 
+      def sqlserver?
+        /sqlserver/i.match?(ActiveRecord::Base.connection.adapter_name)
+      end
+
       # Returns a SQL statement for case/accent (if possible) insensitive match
       def like(left, right, options={})
         neg = (options[:match] == false ? 'NOT ' : '')