diff --git a/CHANGELOG.md b/CHANGELOG.md
index 90cf32a..3671958 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Fixed
+- Add fall back in case of the primary server is not defined. ([@chubchenko][])
+- Require `json` to convert `Hash` object to `JSON`. ([@chubchenko][])
 
 ## [0.1.4] - 2021-07-27
 ### Fixed
diff --git a/lib/capistrano/slacky/on.rb b/lib/capistrano/slacky/on.rb
index a0f42b5..eee5937 100644
--- a/lib/capistrano/slacky/on.rb
+++ b/lib/capistrano/slacky/on.rb
@@ -18,7 +18,9 @@ class Path
       module_function
 
       def on(within:, &block)
-        ::Capistrano::DSL.on(::Capistrano::Configuration.env.primary(:app)) do
+        role = ::Capistrano::Configuration.env.primary(:app) || ::Capistrano::Configuration.env.roles(:all).first
+
+        ::Capistrano::DSL.on(role) do
           ::SSHKit::Backend.current.within(PATH_MAP.fetch(within).call, &block)
         end
       end
diff --git a/lib/capistrano/slacky/payload.rb b/lib/capistrano/slacky/payload.rb
index 7be28eb..e461d6d 100644
--- a/lib/capistrano/slacky/payload.rb
+++ b/lib/capistrano/slacky/payload.rb
@@ -5,6 +5,8 @@
 module Capistrano
   module Slacky
     class Payload
+      require "json"
+
       def initialize(env:, action:)
         @env = env
         @action = action