diff --git a/lib/fastlane_core/configuration/commander_generator.rb b/lib/fastlane_core/configuration/commander_generator.rb
index <HASH>..<HASH> 100644
--- a/lib/fastlane_core/configuration/commander_generator.rb
+++ b/lib/fastlane_core/configuration/commander_generator.rb
@@ -13,8 +13,8 @@ module FastlaneCore
       options.each do |option|
         next if option.description.to_s.length == 0 # "private" options
 
-        appendix = (option.is_string ? "STRING" : "")
-        type = (option.is_string ? String : nil)
+        appendix = (option.string? ? "STRING" : "")
+        type = (option.string? ? String : nil)
         short_option = option.short_option
 
         raise "Short option #{short_option} already taken for key #{option.key}".red if short_codes.include? short_option
diff --git a/lib/fastlane_core/configuration/config_item.rb b/lib/fastlane_core/configuration/config_item.rb
index <HASH>..<HASH> 100644
--- a/lib/fastlane_core/configuration/config_item.rb
+++ b/lib/fastlane_core/configuration/config_item.rb
@@ -89,7 +89,7 @@ module FastlaneCore
     end
 
     # Replaces the attr_accessor, but maintains the same interface
-    def is_string
+    def string?
       data_type == String
     end
Rename the is_string method to fit with styleguide