diff --git a/lib/active_record/configurations.rb b/lib/active_record/configurations.rb
index 9845699..54e2caa 100644
--- a/lib/active_record/configurations.rb
+++ b/lib/active_record/configurations.rb
@@ -32,11 +32,11 @@ def self.establish_connection(config = nil)
 			config ||= DEFAULT_ENV.call.to_sym
 			spec_name = self == Base ? "primary" : name
 			self.connection_specification_name = spec_name
-	
-			resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new(self.configurations)
-			spec = resolver.resolve(config).symbolize_keys
+			
+			spec = self.configurations.fetch(config.to_s, config).symbolize_keys
+			
 			spec[:name] = spec_name
-	
+			
 			connection_handler.establish_connection(spec)
 		end
 	end
@@ -150,4 +150,24 @@ def configure(name, parent: :default, **options, &block)
 			self.configurations[name.to_s] = configuration.stringify_keys
 		end
 	end
+	
+	module ConnectionAdapters
+		class ConnectionSpecification
+			def resolve_symbol_connection(env_name, pool_name)
+				db_config = configurations.find_db_config(env_name)
+
+				if db_config
+					resolve_connection(db_config.config).merge("name" => pool_name.to_s)
+				else
+					raise AdapterNotSpecified, <<~MSG
+						The `#{env_name}` database is not configured for the `#{ActiveRecord::ConnectionHandling::DEFAULT_ENV.call}` environment.
+
+						Available databases configurations are:
+
+						#{build_configuration_sentence}
+					MSG
+				end
+			end
+		end
+	end
 end