diff --git a/lib/puma/cli.rb b/lib/puma/cli.rb
index aa940f84d5..cff30af861 100644
--- a/lib/puma/cli.rb
+++ b/lib/puma/cli.rb
@@ -162,7 +162,7 @@ def setup_options
           end
 
           o.on "--extra-runtime-dependencies GEM1,GEM2", "Defines any extra needed gems when using --prune-bundler" do |arg|
-            c.extra_runtime_dependencies arg.split(',')
+            user_config.extra_runtime_dependencies arg.split(',')
           end
 
           o.on "-q", "--quiet", "Do not log requests internally (default true)" do
diff --git a/test/test_cli.rb b/test/test_cli.rb
index 44d548051d..f4d6474bd4 100644
--- a/test/test_cli.rb
+++ b/test/test_cli.rb
@@ -352,6 +352,17 @@ def test_load_path
     $LOAD_PATH.shift
   end
 
+  def test_extra_runtime_dependencies
+    failed = false
+    begin
+      Puma::CLI.new ['--extra-runtime-dependencies', 'a,b']
+    rescue
+      failed = true
+    end
+
+    refute failed, "failed setting CLI option --extra-runtime-dependencies"
+  end
+
   def test_environment
     ENV.delete 'RACK_ENV'