diff --git a/vite_rails/lib/vite_rails/cli.rb b/vite_rails/lib/vite_rails/cli.rb
index 31418f6a..5b83c072 100644
--- a/vite_rails/lib/vite_rails/cli.rb
+++ b/vite_rails/lib/vite_rails/cli.rb
@@ -31,7 +31,7 @@ def setup_app_files
       replace_first_line config.config_path, "app/frontend", %(    "sourceCodeDir": "#{dir}",)
     end
     setup_content_security_policy root.join("config/initializers/content_security_policy.rb")
-    append root.join("Procfile.dev"), "web: bin/rails s"
+    append_unless_present root.join("Procfile.dev"), "web: bin/rails s", pattern: "web:"
   end
 
   # Internal: Configure CSP rules that allow to load @vite/client correctly.
diff --git a/vite_ruby/lib/vite_ruby/cli/file_utils.rb b/vite_ruby/lib/vite_ruby/cli/file_utils.rb
index 35afb796..36763868 100644
--- a/vite_ruby/lib/vite_ruby/cli/file_utils.rb
+++ b/vite_ruby/lib/vite_ruby/cli/file_utils.rb
@@ -32,8 +32,15 @@ def cp(source, destination)
     # @since 1.2.11
     # @api private
     def append(path, contents)
+      append_unless_present(path, contents, pattern: contents)
+    end
+
+    # Adds a new line at the bottom of the file, unless any line matches the pattern.
+    #
+    # @api private
+    def append_unless_present(path, contents, pattern:)
       content = read_lines(path)
-      return if content.join.include?(contents)
+      return if content.any? { |line| line.include?(pattern) }
 
       content << "\n" unless content.last&.end_with?("\n")
       content << "#{contents}\n"
diff --git a/vite_ruby/lib/vite_ruby/cli/install.rb b/vite_ruby/lib/vite_ruby/cli/install.rb
index e3f9c820..1e1fda63 100644
--- a/vite_ruby/lib/vite_ruby/cli/install.rb
+++ b/vite_ruby/lib/vite_ruby/cli/install.rb
@@ -61,7 +61,7 @@ def install_sample_files
 
   def_delegators "ViteRuby", :config
 
-  %i[append cp inject_line_after inject_line_after_last inject_line_before replace_first_line write].each do |util|
+  %i[append append_unless_present cp inject_line_after inject_line_after_last inject_line_before replace_first_line write].each do |util|
     define_method(util) { |*args|
       ViteRuby::CLI::FileUtils.send(util, *args) rescue nil
     }