diff --git a/library.json b/library.json
index b78099b..6c72399 100644
--- a/library.json
+++ b/library.json
@@ -1,6 +1,6 @@
 {
     "name" : "CoAP simple library",
-    "version" : "1.3.20",
+    "version" : "1.3.21",
     "description" : "Simple CoAP client/server library for generic Arduino Client hardware.",
     "keywords" : "communication, coap, wifi",
     "authors" : {
diff --git a/library.properties b/library.properties
index 8760932..8992996 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=CoAP simple library
-version=1.3.20
+version=1.3.21
 author=Hirotaka Niisato <hirotakaster@gmail.com>
 maintainer=Hirotaka Niisato <hirotakaster@gmail.com>
 sentence=Simple CoAP client/server library for generic Arduino Client hardware.