diff --git a/js/libtextsecure.js b/js/libtextsecure.js
index 4627482d..e64ad520 100644
--- a/js/libtextsecure.js
+++ b/js/libtextsecure.js
@@ -38829,7 +38829,7 @@ function Message(options) {
         throw new Error('Invalid timestamp');
     }
 
-    if (this.expireTimer !== undefined) {
+    if (this.expireTimer !== undefined && this.expireTimer !== null) {
         if (typeof this.expireTimer !== 'number' || !(this.expireTimer >= 0)) {
             throw new Error('Invalid expireTimer');
         }
diff --git a/libtextsecure/sendmessage.js b/libtextsecure/sendmessage.js
index f2c90e47..b5027c70 100644
--- a/libtextsecure/sendmessage.js
+++ b/libtextsecure/sendmessage.js
@@ -36,7 +36,7 @@ function Message(options) {
         throw new Error('Invalid timestamp');
     }
 
-    if (this.expireTimer !== undefined) {
+    if (this.expireTimer !== undefined && this.expireTimer !== null) {
         if (typeof this.expireTimer !== 'number' || !(this.expireTimer >= 0)) {
             throw new Error('Invalid expireTimer');
         }