diff --git a/library.properties b/library.properties
index e71740b..d10fb01 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=Adafruit IO Arduino
-version=3.9.1
+version=4.0.0
 author=Adafruit
 maintainer=Adafruit <adafruitio@adafruit.com>
 sentence=Arduino library to access Adafruit IO.