diff --git a/lib/puma/launcher.rb b/lib/puma/launcher.rb
index 48867b2c85..327d8dd6ab 100644
--- a/lib/puma/launcher.rb
+++ b/lib/puma/launcher.rb
@@ -165,10 +165,10 @@ def phased_restart
     def run
       previous_env =
         if defined?(Bundler)
-          env = Bundler::ORIGINAL_ENV
+          env = Bundler::ORIGINAL_ENV.dup
           # add -rbundler/setup so we load from Gemfile when restarting
           bundle = "-rbundler/setup"
-          env["RUBYOPT"] = [env["RUBYOPT"], bundle].join(" ") unless env["RUBYOPT"].include?(bundle)
+          env["RUBYOPT"] = [env["RUBYOPT"], bundle].join(" ") unless env["RUBYOPT"].to_s.include?(bundle)
           env
         else
           ENV.to_h