diff --git a/lib/inboxable.rb b/lib/inboxable.rb
index 704fe37..87a4b20 100644
--- a/lib/inboxable.rb
+++ b/lib/inboxable.rb
@@ -9,10 +9,10 @@ class Error < StandardError; end
 
   class << self
     attr_accessor :configuration
-  end
 
-  def self.configure
-    @configuration ||= Configuration.new
-    yield(@configuration) if block_given?
+    def configure
+      @configuration ||= Configuration.new
+      yield(@configuration) if block_given?
+    end
   end
 end
diff --git a/sig/inboxable.rbs b/sig/inboxable.rbs
index b2e9082..91f7503 100644
--- a/sig/inboxable.rbs
+++ b/sig/inboxable.rbs
@@ -1,5 +1,5 @@
 module Inboxable
   VERSION: String
   attr_accessor configuration: Configuration
-  def configure: () { (Configuration) -> Configuration } -> Configuration
+  def self.configure: () { (Configuration) -> Configuration } -> Configuration
 end