diff --git a/Gemfile b/Gemfile
index eefd680..d86ba4a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,8 +1,7 @@
-source 'https://rubygems.org'
-
-gem 'rails'
+source "https://rubygems.org"
 
 group :development, :test do
+  gem "rails", "~> 6"
   gem "rspec-rails", "~> 3"
   gem "pry", "~> 0"
 end
diff --git a/README.md b/README.md
index 8575013..724cb4e 100644
--- a/README.md
+++ b/README.md
@@ -114,11 +114,12 @@ two environment variables to use this protocol:
 format. This environment variable will be the contents of a `.pub` file,
 newlines and all.
 
-`CHATOPS_AUTH_BASE_URL` is the base URL of your server as the chatops client
+`CHATOPS_AUTH_BASE_URL` is the base URLs of your servers as the chatops client
 sees it. This is specified as an environment variable since rails will trust
 client headers about a forwarded hostname. For example, if your chatops client
 has added the url `https://example.com/_chatops`, you'd set this to
-`https://example.com`.
+`https://example.com`. You can specify more than one base url divided by comma,
+e.g. `https://example.com,https://example2.com`
 
 You can also optionally set `CHATOPS_AUTH_ALT_PUBLIC_KEY` to a second public key
 which will be accepted. This is helpful when rolling keys.
diff --git a/chatops-controller.gemspec b/chatops-controller.gemspec
index fda8ee0..ce5e50c 100644
--- a/chatops-controller.gemspec
+++ b/chatops-controller.gemspec
@@ -17,6 +17,7 @@ Gem::Specification.new do |s|
   s.files = Dir["{app,config,db,lib}/**/*", "README.md"]
   s.test_files = Dir["spec/**/*"]
 
+  s.add_dependency "rails"
   s.add_dependency "actionpack", ">= 6.0"
   s.add_dependency "activesupport", ">= 6.0"
 
diff --git a/lib/chatops.rb b/lib/chatops.rb
index b95e747..fa7d90c 100644
--- a/lib/chatops.rb
+++ b/lib/chatops.rb
@@ -23,8 +23,8 @@ def self.alt_public_key
     ENV["CHATOPS_AUTH_ALT_PUBLIC_KEY"]
   end
 
-  def self.auth_base_url
-    ENV[auth_base_url_env_var_name]
+  def self.auth_base_urls
+    ENV.fetch(auth_base_url_env_var_name, "").split(",").map(&:strip)
   end
 
   def self.auth_base_url_env_var_name
diff --git a/lib/chatops/controller.rb b/lib/chatops/controller.rb
index 72aa8fe..8280eed 100644
--- a/lib/chatops/controller.rb
+++ b/lib/chatops/controller.rb
@@ -118,26 +118,29 @@ def ensure_user_given
     end
 
     def ensure_chatops_authenticated
-      body = request.raw_post || ""
-      signature_string = [@chatops_url, @chatops_nonce, @chatops_timestamp, body].join("\n")
-      # We return this just to aid client debugging.
-      response.headers["Chatops-Signature-String"] = Base64.strict_encode64(signature_string)
       raise ConfigurationError.new("You need to add a client's public key in .pem format via #{Chatops.public_key_env_var_name}") unless Chatops.public_key.present?
-      if signature_valid?(Chatops.public_key, @chatops_signature, signature_string) ||
-          signature_valid?(Chatops.alt_public_key, @chatops_signature, signature_string)
+
+      body = request.raw_post || ""
+
+      @chatops_urls.each do |url|
+        signature_string = [url, @chatops_nonce, @chatops_timestamp, body].join("\n")
+        # We return this just to aid client debugging.
+        response.headers["Chatops-Signature-String"] = Base64.strict_encode64(signature_string)
+        if signature_valid?(Chatops.public_key, @chatops_signature, signature_string) ||
+            signature_valid?(Chatops.alt_public_key, @chatops_signature, signature_string)
           return true
+        end
       end
+
       return jsonrpc_error(-32800, 403, "Not authorized")
     end
 
     def ensure_valid_chatops_url
-      unless Chatops.auth_base_url.present?
+      unless Chatops.auth_base_urls.present?
         raise ConfigurationError.new("You need to set the server's base URL to authenticate chatops RPC via #{Chatops.auth_base_url_env_var_name}")
       end
-      if Chatops.auth_base_url[-1] == "/"
-        raise ConfigurationError.new("Don't include a trailing slash in #{Chatops.auth_base_url_env_var_name}; the rails path will be appended and it must match exactly.")
-      end
-      @chatops_url = Chatops.auth_base_url + request.path
+
+      @chatops_urls = Chatops.auth_base_urls.map { |url| url.chomp("/") + request.path }
     end
 
     def ensure_valid_chatops_nonce
diff --git a/spec/lib/chatops/controller_spec.rb b/spec/lib/chatops/controller_spec.rb
index 6225af3..591c6fc 100644
--- a/spec/lib/chatops/controller_spec.rb
+++ b/spec/lib/chatops/controller_spec.rb
@@ -56,7 +56,7 @@ def ensure_app_given
 
     @private_key = OpenSSL::PKey::RSA.new(2048)
     ENV["CHATOPS_AUTH_PUBLIC_KEY"] = @private_key.public_key.to_pem
-    ENV["CHATOPS_AUTH_BASE_URL"] = "http://test.host"
+    ENV["CHATOPS_AUTH_BASE_URL"] = "http://old.host,http://test.host/"
   end
 
   def rails_flexible_post(path, outer_params, jsonrpc_params = nil)
@@ -315,7 +315,7 @@ def rails_flexible_post(path, outer_params, jsonrpc_params = nil)
         :room_id => "#someroom",
         :unknown_key => "few" # This should get ignored
       }, {
-       "app" => "foo" 
+       "app" => "foo"
       }
       expect(json_response).to eq({
         "jsonrpc" => "2.0",
@@ -323,7 +323,7 @@ def rails_flexible_post(path, outer_params, jsonrpc_params = nil)
         "result" => "{\"params\":{\"action\":\"proxy_parameters\",\"chatop\":\"proxy_parameters\",\"controller\":\"anonymous\",\"mention_slug\":\"mention_slug_here\",\"message_id\":\"message_id_here\",\"room_id\":\"#someroom\",\"user\":\"foo\"},\"jsonrpc_params\":{\"app\":\"foo\"}}"
       })
       expect(response.status).to eq 200
-    end 
+    end
 
 
     it "uses typical controller fun like before_action" do