diff --git a/.rubocop.yml b/.rubocop.yml
index 2f7db8d..d4afbe6 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -4,6 +4,14 @@ plugins:
 AllCops:
   NewCops: enable
 
+# rubocop needs manual exclude each rule; why???
+Style/Documentation:
+  Exclude:
+    - "**/*.rbs"
+Style/FrozenStringLiteralComment:
+  Exclude:
+    - "**/*.rbs"
+
 Style/StringLiterals:
   Enabled: true
   EnforcedStyle: single_quotes
diff --git a/sig/_private/internal.rbs b/sig/_private/internal.rbs
new file mode 100644
index 0000000..2be1140
--- /dev/null
+++ b/sig/_private/internal.rbs
@@ -0,0 +1,7 @@
+# 存在しないmoduleを定義したくないのでトップレベルのtypeを許可
+# rubocop:disable RBS/Lint/TopLevelTypeAlias
+
+type pin = Integer | String
+type id = Integer | String
+
+# rubocop:enable all
diff --git a/sig/adc.rbs b/sig/adc.rbs
index b4de83b..a025833 100644
--- a/sig/adc.rbs
+++ b/sig/adc.rbs
@@ -1,6 +1,4 @@
 class ADC
-  type pin = Integer | String
-
   def initialize: (pin pin, *untyped params) -> void
 
   def read_voltage: () -> Float
diff --git a/sig/gpio.rbs b/sig/gpio.rbs
index f0f5f91..94bf3bf 100644
--- a/sig/gpio.rbs
+++ b/sig/gpio.rbs
@@ -23,8 +23,6 @@ class GPIO
   # オープンドレインモードに設定する
   OPEN_DRAIN: _Mode
 
-  type pin = Integer | String
-
   # @param pin 使用する物理ピン\
   # @param params モードの指定\
   # @example
diff --git a/sig/i2c.rbs b/sig/i2c.rbs
index 3bbac8b..8d782a2 100644
--- a/sig/i2c.rbs
+++ b/sig/i2c.rbs
@@ -1,10 +1,10 @@
 class I2C
   def initialize: (
-    ?Integer? id,
+    ?id? id,
     ?frequency: Integer,
     ?freq: Integer,
-    ?scl_pin: Integer,
-    ?sda_pin: Integer
+    ?scl_pin: pin,
+    ?sda_pin: pin
   ) -> void
 
   def read: (Integer i2c_adrs_7, Integer read_bytes, *(Integer | Array[Integer] | String) params) -> String
diff --git a/sig/pwm.rbs b/sig/pwm.rbs
index 155e76d..2413159 100644
--- a/sig/pwm.rbs
+++ b/sig/pwm.rbs
@@ -1,6 +1,4 @@
 class PWM
-  type pin = Integer | String
-
   def initialize: (
     pin pin,
     ?frequency: Integer | Float,
diff --git a/sig/spi.rbs b/sig/spi.rbs
index 6809189..5df27df 100644
--- a/sig/spi.rbs
+++ b/sig/spi.rbs
@@ -11,8 +11,8 @@ class SPI
   type mode = 0 | 1 | 2 | 3
 
   def initialize: (
-    ?Integer? id,
-    ?unit: Integer,
+    ?id? id,
+    ?unit: id,
     ?frequency: Integer,
     ?mode: mode,
     ?first_bit: first_bit
diff --git a/sig/uart.rbs b/sig/uart.rbs
index eeb6bb1..928b854 100644
--- a/sig/uart.rbs
+++ b/sig/uart.rbs
@@ -11,9 +11,6 @@ class UART
 
   RTSCTS: parameter
 
-  type id = Integer | String
-  type pin = Integer | String
-
   def initialize: (
     ?id? id,
     ?baudrate: Integer,