diff --git a/app/controllers/journals_controller.rb b/app/controllers/journals_controller.rb
index f7b821312..cbf545187 100644
--- a/app/controllers/journals_controller.rb
+++ b/app/controllers/journals_controller.rb
@@ -68,11 +68,11 @@ class JournalsController < ApplicationController
     if @journal
       user = @journal.user
       text = @journal.notes
-      @content = +"#{ll(Setting.default_language, :text_user_wrote_in, {:value => user, :link => "#note-#{params[:journal_indice]}"})}\n> "
+      @content = "#{ll(Setting.default_language, :text_user_wrote_in, {:value => user, :link => "#note-#{params[:journal_indice]}"})}\n> "
     else
       user = @issue.author
       text = @issue.description
-      @content = +"#{ll(Setting.default_language, :text_user_wrote, user)}\n> "
+      @content = "#{ll(Setting.default_language, :text_user_wrote, user)}\n> "
     end
     # Replaces pre blocks with [...]
     text = text.to_s.strip.gsub(%r{<pre>(.*?)</pre>}m, '[...]')
diff --git a/app/controllers/messages_controller.rb b/app/controllers/messages_controller.rb
index 769cdff67..5050d94a7 100644
--- a/app/controllers/messages_controller.rb
+++ b/app/controllers/messages_controller.rb
@@ -120,9 +120,9 @@ class MessagesController < ApplicationController
     @subject = "RE: #{@subject}" unless @subject.starts_with?('RE:')
 
     if @message.root == @message
-      @content = +"#{ll(Setting.default_language, :text_user_wrote, @message.author)}\n> "
+      @content = "#{ll(Setting.default_language, :text_user_wrote, @message.author)}\n> "
     else
-      @content = +"#{ll(Setting.default_language, :text_user_wrote_in, {:value => @message.author, :link => "message##{@message.id}"})}\n> "
+      @content = "#{ll(Setting.default_language, :text_user_wrote_in, {:value => @message.author, :link => "message##{@message.id}"})}\n> "
     end
     @content << @message.content.to_s.strip.gsub(%r{<pre>(.*?)</pre>}m, '[...]').gsub(/(\r?\n|\r\n?)/, "\n> ") + "\n\n"
 
diff --git a/app/controllers/repositories_controller.rb b/app/controllers/repositories_controller.rb
index 08fa8c2d1..9be7878ce 100644
--- a/app/controllers/repositories_controller.rb
+++ b/app/controllers/repositories_controller.rb
@@ -264,7 +264,7 @@ class RepositoriesController < ApplicationController
     if params[:format] == 'diff'
       @diff = @repository.diff(@path, @rev, @rev_to)
       (show_error_not_found; return) unless @diff
-      filename = +"changeset_r#{@rev}"
+      filename = "changeset_r#{@rev}"
       filename << "_r#{@rev_to}" if @rev_to
       send_data @diff.join, :filename => "#{filename}.diff",
                             :type => 'text/x-patch',
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 5e873fe62..49e8b0a82 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -361,7 +361,7 @@ module ApplicationHelper
   end
 
   def toggle_link(name, id, options={})
-    onclick = +"$('##{id}').toggle(); "
+    onclick = "$('##{id}').toggle(); "
     onclick << (options[:focus] ? "$('##{options[:focus]}:visible').focus(); " : "this.blur(); ")
     onclick << "$(window).scrollTop($('##{options[:focus]}').position().top); " if options[:scroll]
     onclick << "return false;"
@@ -1479,7 +1479,7 @@ module ApplicationHelper
         div_class = +'toc'
         div_class << ' right' if right_align
         div_class << ' left' if left_align
-        out = +"<ul class=\"#{div_class}\"><li><strong>#{l :label_table_of_contents}</strong></li><li>"
+        out = "<ul class=\"#{div_class}\"><li><strong>#{l :label_table_of_contents}</strong></li><li>"
         root = headings.map(&:first).min
         current = root
         started = false
diff --git a/app/helpers/issues_helper.rb b/app/helpers/issues_helper.rb
index c92dd75e7..88c98f90d 100644
--- a/app/helpers/issues_helper.rb
+++ b/app/helpers/issues_helper.rb
@@ -96,7 +96,7 @@ module IssuesHelper
       issue.descendants.visible.
         preload(:status, :priority, :tracker,
                 :assigned_to).sort_by(&:lft)) do |child, level|
-      css = +"issue issue-#{child.id} hascontextmenu #{child.css_classes}"
+      css = "issue issue-#{child.id} hascontextmenu #{child.css_classes}"
       css << " idnt idnt-#{level}" if level > 0
       buttons =
         if manage_relations
diff --git a/app/helpers/wiki_helper.rb b/app/helpers/wiki_helper.rb
index 38a650ed0..e00b3686e 100644
--- a/app/helpers/wiki_helper.rb
+++ b/app/helpers/wiki_helper.rb
@@ -25,7 +25,7 @@ module WikiHelper
     s = (+'').html_safe
     if pages.has_key?(parent)
       pages[parent].each do |page|
-        attrs = +"value='#{page.id}'"
+        attrs = "value='#{page.id}'"
         attrs << " selected='selected'" if selected == page
         indent = (level > 0) ? ('&nbsp;' * level * 2 + '&#187; ') : ''
 
diff --git a/app/models/issue.rb b/app/models/issue.rb
index 369d7c1a6..9b47ce7bd 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -1459,7 +1459,7 @@ class Issue < ApplicationRecord
 
   # Returns a string of css classes that apply to the issue
   def css_classes(user=User.current)
-    s = +"issue tracker-#{tracker_id} status-#{status_id} #{priority.try(:css_classes)}"
+    s = "issue tracker-#{tracker_id} status-#{status_id} #{priority.try(:css_classes)}"
     s << ' closed' if closed?
     s << ' overdue' if overdue?
     s << ' child' if child?
diff --git a/app/models/principal.rb b/app/models/principal.rb
index 59aac3078..77f599c73 100644
--- a/app/models/principal.rb
+++ b/app/models/principal.rb
@@ -72,7 +72,7 @@ class Principal < ApplicationRecord
       where({})
     else
       pattern = "%#{sanitize_sql_like q}%"
-      sql = +"LOWER(#{table_name}.login) LIKE LOWER(:p) ESCAPE :s"
+      sql = "LOWER(#{table_name}.login) LIKE LOWER(:p) ESCAPE :s"
       sql << " OR #{table_name}.id IN (SELECT user_id FROM #{EmailAddress.table_name} WHERE LOWER(address) LIKE LOWER(:p) ESCAPE :s)"
       params = {:p => pattern, :s => '\\'}
 
diff --git a/lib/redmine/scm/adapters/subversion_adapter.rb b/lib/redmine/scm/adapters/subversion_adapter.rb
index f0e6722f0..c4bb31148 100644
--- a/lib/redmine/scm/adapters/subversion_adapter.rb
+++ b/lib/redmine/scm/adapters/subversion_adapter.rb
@@ -60,7 +60,7 @@ module Redmine
 
         # Get info about the svn repository
         def info
-          cmd = +"#{self.class.sq_bin} info --xml #{target}"
+          cmd = "#{self.class.sq_bin} info --xml #{target}"
           cmd << credentials_string
           info = nil
           shellout(cmd) do |io|
@@ -98,7 +98,7 @@ module Redmine
           path ||= ''
           identifier = (identifier and identifier.to_i > 0) ? identifier.to_i : "HEAD"
           entries = Entries.new
-          cmd = +"#{self.class.sq_bin} list --xml #{target(path)}@#{identifier}"
+          cmd = "#{self.class.sq_bin} list --xml #{target(path)}@#{identifier}"
           cmd << credentials_string
           shellout(cmd) do |io|
             output = io.read.force_encoding('UTF-8')
@@ -146,7 +146,7 @@ module Redmine
           return nil unless self.class.client_version_above?([1, 5, 0])
 
           identifier = (identifier and identifier.to_i > 0) ? identifier.to_i : "HEAD"
-          cmd = +"#{self.class.sq_bin} proplist --verbose --xml #{target(path)}@#{identifier}"
+          cmd = "#{self.class.sq_bin} proplist --verbose --xml #{target(path)}@#{identifier}"
           cmd << credentials_string
           properties = {}
           shellout(cmd) do |io|
@@ -169,7 +169,7 @@ module Redmine
           identifier_from = (identifier_from && identifier_from.to_i > 0) ? identifier_from.to_i : "HEAD"
           identifier_to = (identifier_to && identifier_to.to_i > 0) ? identifier_to.to_i : 1
           revisions = Revisions.new
-          cmd = +"#{self.class.sq_bin} log --xml -r #{identifier_from}:#{identifier_to}"
+          cmd = "#{self.class.sq_bin} log --xml -r #{identifier_from}:#{identifier_to}"
           cmd << credentials_string
           cmd << " --verbose " if  options[:with_paths]
           cmd << " --limit #{options[:limit].to_i}" if options[:limit]
@@ -218,7 +218,7 @@ module Redmine
 
           identifier_to = (identifier_to and identifier_to.to_i > 0) ? identifier_to.to_i : (identifier_from.to_i - 1)
 
-          cmd = +"#{self.class.sq_bin} diff -r "
+          cmd = "#{self.class.sq_bin} diff -r "
           cmd << "#{identifier_to}:"
           cmd << "#{identifier_from}"
           cmd << " #{target(path)}@#{identifier_from}"
@@ -236,7 +236,7 @@ module Redmine
 
         def cat(path, identifier=nil)
           identifier = (identifier and identifier.to_i > 0) ? identifier.to_i : "HEAD"
-          cmd = +"#{self.class.sq_bin} cat #{target(path)}@#{identifier}"
+          cmd = "#{self.class.sq_bin} cat #{target(path)}@#{identifier}"
           cmd << credentials_string
           cat = nil
           shellout(cmd) do |io|
@@ -250,7 +250,7 @@ module Redmine
 
         def annotate(path, identifier=nil)
           identifier = (identifier and identifier.to_i > 0) ? identifier.to_i : "HEAD"
-          cmd = +"#{self.class.sq_bin} blame #{target(path)}@#{identifier}"
+          cmd = "#{self.class.sq_bin} blame #{target(path)}@#{identifier}"
           cmd << credentials_string
           blame = Annotate.new
           shellout(cmd) do |io|
diff --git a/lib/redmine/wiki_formatting/textile/redcloth3.rb b/lib/redmine/wiki_formatting/textile/redcloth3.rb
index f6e738786..71261334c 100644
--- a/lib/redmine/wiki_formatting/textile/redcloth3.rb
+++ b/lib/redmine/wiki_formatting/textile/redcloth3.rb
@@ -580,9 +580,9 @@ class RedCloth3 < String
                         depth << tl
                         atts = pba(atts)
                         atts = shelve(atts) if atts
-                        lines[line_id] = +"\t<#{lT(tl)}l#{atts}>\n\t<li>#{content}"
+                        lines[line_id] = "\t<#{lT(tl)}l#{atts}>\n\t<li>#{content}"
                     else
-                        lines[line_id] = +"\t\t<li>#{content}"
+                        lines[line_id] = "\t\t<li>#{content}"
                     end
                     last_line = line_id
                 else
@@ -632,7 +632,7 @@ class RedCloth3 < String
         text.gsub!(CODE_RE) do |m|
             before, lang, code, after = $~[1..4]
             lang = " lang=\"#{lang}\"" if lang
-            rip_offtags(+"#{before}<code#{lang}>#{code}</code>#{after}", false)
+            rip_offtags("#{before}<code#{lang}>#{code}</code>#{after}", false)
         end
     end
 
@@ -844,7 +844,7 @@ class RedCloth3 < String
             next all unless uri_with_link_safe_scheme?(url)
 
             atts = pba(atts)
-            atts = +" href=\"#{url}#{slash}\"#{atts}"
+            atts = " href=\"#{url}#{slash}\"#{atts}"
             atts << " title=\"#{htmlesc title}\"" if title
             atts = shelve(atts) if atts
             external = (url =~ /^https?:\/\//) ? ' class="external"' : ''
@@ -953,7 +953,7 @@ class RedCloth3 < String
             stln, algn, atts, url, title, href, href_a1, href_a2 = $~[1..8]
             htmlesc title
             atts = pba(atts)
-            atts = +" src=\"#{htmlesc url.dup}\"#{atts}"
+            atts = " src=\"#{htmlesc url.dup}\"#{atts}"
             atts << " title=\"#{title}\"" if title
             atts << " alt=\"#{title}\""
             # size = @getimagesize($url);
@@ -1099,12 +1099,12 @@ class RedCloth3 < String
                         ### NB: some changes were made not to use $N variables, because we use "match"
                         ###   and it breaks following lines
                         htmlesc(aftertag, :NoQuotes) if aftertag && escape_aftertag && !first.match(/<code\s+class="(\w+)">/)
-                        line = +"<redpre##{@pre_list.length}>"
+                        line = "<redpre##{@pre_list.length}>"
                         first =~ /<#{OFFTAGS}([^>]*)>/o
                         tag = $1
                         $2.to_s =~ /(class\=("[^"]+"|'[^']+'))/i
                         tag << " #{$1}" if $1 && tag == 'code'
-                        @pre_list << +"<#{tag}>#{aftertag}"
+                        @pre_list << "<#{tag}>#{aftertag}"
                     end
                 elsif $1 and codepre > 0
                     if codepre - used_offtags.length > 0
diff --git a/test/unit/repository_test.rb b/test/unit/repository_test.rb
index 520786f2f..63aa43d35 100644
--- a/test/unit/repository_test.rb
+++ b/test/unit/repository_test.rb
@@ -310,7 +310,7 @@ class RepositoryTest < ActiveSupport::TestCase
         )
     long_whitespace = "                                                "
     expected_comment = "This is a loooooooooooooooooooooooooooong comment"
-    comment = +"#{expected_comment}#{long_whitespace}\n"
+    comment = "#{expected_comment}#{long_whitespace}\n"
     3.times {comment << "#{long_whitespace}\n"}
     changeset = Changeset.new(
       :comments => comment, :commit_date => Time.now,