diff --git a/lib/arduino_firmata/const.rb b/lib/arduino_firmata/const.rb
index 5558e04..6778e76 100644
--- a/lib/arduino_firmata/const.rb
+++ b/lib/arduino_firmata/const.rb
@@ -18,15 +18,16 @@ class Status
     OPEN = 1
   end
 
-  INPUT  = 0
-  OUTPUT = 1
-  ANALOG = 2
-  PWM    = 3
-  SERVO  = 4
-  SHIFT  = 5
-  I2C    = 6
-  LOW    = 0
-  HIGH   = 1
+  INPUT         = 0
+  OUTPUT        = 1
+  ANALOG        = 2
+  PWM           = 3
+  SERVO         = 4
+  SHIFT         = 5
+  I2C           = 6
+  INPUT_PULLUP  = 11
+  LOW           = 0
+  HIGH          = 1
 
   MAX_DATA_BYTES  = 32
   DIGITAL_MESSAGE = 0x90 # send data for a digital port
diff --git a/test/test_arduino_firmata.rb b/test/test_arduino_firmata.rb
index 1357174..45f05a7 100644
--- a/test/test_arduino_firmata.rb
+++ b/test/test_arduino_firmata.rb
@@ -51,7 +51,11 @@ def test_servo_write
 
   def test_pin_mode
     0.upto(13).each do |pin|
-      mode = [ArduinoFirmata::OUTPUT, ArduinoFirmata::INPUT].sample
+      mode = [
+        ArduinoFirmata::OUTPUT,
+        ArduinoFirmata::INPUT,
+        ArduinoFirmata::INPUT_PULLUP
+      ].sample
       assert @arduino.pin_mode(pin, mode) == mode
     end
   end