diff --git a/keyserver/src/session/viewer.js b/keyserver/src/session/viewer.js
--- a/keyserver/src/session/viewer.js
+++ b/keyserver/src/session/viewer.js
@@ -147,7 +147,7 @@
     }
   }
 
-  setDeviceToken(deviceToken: string) {
+  setDeviceToken(deviceToken: ?string) {
     if (this.data.loggedIn) {
       this.data = { ...this.data, deviceToken };
     } else {
diff --git a/keyserver/src/updaters/device-token-updaters.js b/keyserver/src/updaters/device-token-updaters.js
--- a/keyserver/src/updaters/device-token-updaters.js
+++ b/keyserver/src/updaters/device-token-updaters.js
@@ -14,12 +14,15 @@
   if (deviceType === undefined) {
     throw new ServerError('invalid_parameters');
   }
+  const { deviceToken } = update;
 
-  viewer.setDeviceToken(update.deviceToken);
-  await clearDeviceToken(update.deviceToken);
+  viewer.setDeviceToken(deviceToken);
+  if (deviceToken) {
+    await clearDeviceToken(deviceToken);
+  }
 
   const setColumns = {};
-  setColumns.device_token = update.deviceToken;
+  setColumns.device_token = deviceToken;
   setColumns.platform = deviceType;
   if (update.platformDetails) {
     const { platform, ...versions } = update.platformDetails;
diff --git a/lib/types/device-types.js b/lib/types/device-types.js
--- a/lib/types/device-types.js
+++ b/lib/types/device-types.js
@@ -30,7 +30,7 @@
 }
 
 export type DeviceTokenUpdateRequest = {
-  +deviceToken: string,
+  +deviceToken: ?string,
   +deviceType?: DeviceType,
   +platformDetails?: PlatformDetails,
 };