diff --git a/lib/github_changelog_generator/generator/generator.rb b/lib/github_changelog_generator/generator/generator.rb
index 143d60e8..ff2227f4 100644
--- a/lib/github_changelog_generator/generator/generator.rb
+++ b/lib/github_changelog_generator/generator/generator.rb
@@ -76,7 +76,7 @@ def generate_entry_between_tags(older_tag, newer_tag)
 
       if newer_tag.nil? && filtered_issues.empty? && filtered_pull_requests.empty?
         # do not generate empty unreleased section
-        return ""
+        return +""
       end
 
       newer_tag_link, newer_tag_name, newer_tag_time = detect_link_tag_time(newer_tag)
@@ -128,7 +128,7 @@ def generate_entries_for_all_tags
     end
 
     def generate_unreleased_entry
-      entry = ""
+      entry = +""
       if options[:unreleased]
         start_tag        = @filtered_tags[0] || @sorted_tags.last
         unreleased_entry = generate_entry_between_tags(start_tag, nil)
@@ -166,7 +166,7 @@ def remove_old_fixed_string(log)
     # messages of the same wording are removed.
     # @param log [String]
     def insert_fixed_string(log)
-      ins = ""
+      ins = +""
       ins += @options[:frontmatter] if @options[:frontmatter]
       ins += "#{@options[:header]}\n\n"
       log.insert(0, ins)
diff --git a/lib/github_changelog_generator/generator/section.rb b/lib/github_changelog_generator/generator/section.rb
index e321a4a7..f06c8e38 100644
--- a/lib/github_changelog_generator/generator/section.rb
+++ b/lib/github_changelog_generator/generator/section.rb
@@ -39,7 +39,7 @@ def initialize(opts = {})
     #
     # @return [String] Generated section content
     def generate_content
-      content = ""
+      content = +""
 
       if @issues.any?
         content += "#{@prefix}\n\n" unless @options[:simple_list] || @prefix.blank?