diff --git a/lib/puma/launcher.rb b/lib/puma/launcher.rb
index ea1c301e26..58b51a3d5e 100644
--- a/lib/puma/launcher.rb
+++ b/lib/puma/launcher.rb
@@ -165,10 +165,16 @@ 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)
+          
+          # bundler init ORIGINAL_ENV from ENV before it sets RUBYOPT in ENV, so env["RUBYOPT"] can be nil
+          if env["RUBYOPT"]
+            env["RUBYOPT"] = [env["RUBYOPT"], bundle].join(" ") unless env["RUBYOPT"].include?(bundle)
+          else
+            env["RUBYOPT"] = bundle
+          end
           env
         else
           ENV.to_h