diff --git a/tool/downloader.rb b/tool/downloader.rb
index b623bc3766..59bfd55f17 100644
--- a/tool/downloader.rb
+++ b/tool/downloader.rb
@@ -424,8 +424,8 @@ if $0 == __FILE__
     when '-u', '--update', '--if-modified'
       ## -u, --update, --if-modified  Download newer files only.
       since = true
-    when '-n', '--dryrun'
-      ## -n, --dryrun  Do not download actually.
+    when '-n', '--dry-run', '--dryrun'
+      ## -n, --dry-run  Do not download actually.
       options[:dryrun] = true
     when '--cache-dir'
       ## --cache-dir DIRECTORY  Cache downloaded files in the directory.
diff --git a/tool/outdate-bundled-gems.rb b/tool/outdate-bundled-gems.rb
index 5422aec454..c82d31d743 100755
--- a/tool/outdate-bundled-gems.rb
+++ b/tool/outdate-bundled-gems.rb
@@ -9,8 +9,8 @@ until ARGV.empty?
   when '--'
     ARGV.shift
     break
-  when '-n', '--dryrun'
-    ## -n, --dryrun  Don't remove
+  when '-n', '--dry-run', '--dryrun'
+    ## -n, --dry-run  Don't remove
     fu = FileUtils::DryRun
   when /\A--make=/
     # just to run when `make -n`