diff --git a/README.md b/README.md
index 714ed2c1..ea92c187 100644
--- a/README.md
+++ b/README.md
@@ -63,7 +63,8 @@ var eventHandlers = {
 
 var options = {
   'eventHandlers'    : eventHandlers,
-  'mediaConstraints' : { 'audio': true, 'video': true }
+  'mediaConstraints' : { 'audio': true, 'video': true },
+  'callId'           : 'a84b4c76e66710'
 };
 
 var session = ua.call('sip:bob@example.com', options);
diff --git a/lib/Config.js b/lib/Config.js
index 46f929e4..7c8daf5f 100644
--- a/lib/Config.js
+++ b/lib/Config.js
@@ -21,6 +21,8 @@ exports.settings = {
 
   // SIP instance id (GRUU).
   instance_id : null,
+  // Default Call-ID for REGISTER.
+  call_id : null,
 
   // Preloaded SIP Route header field.
   use_preloaded_route : false,
@@ -204,6 +206,10 @@ const checks = {
         return instance_id;
       }
     },
+    call_id(call_id)
+    {
+      return String(call_id);
+    },
 
     no_answer_timeout(no_answer_timeout)
     {
diff --git a/lib/Message.d.ts b/lib/Message.d.ts
index 8ee3685c..36315304 100644
--- a/lib/Message.d.ts
+++ b/lib/Message.d.ts
@@ -27,6 +27,7 @@ export interface SendMessageOptions extends ExtraHeaders {
   eventHandlers?: Partial<MessageEventMap>;
   fromUserName?: string;
   fromDisplayName?: string;
+  callId?: string;
 }
 
 export class Message extends EventEmitter {
diff --git a/lib/Message.js b/lib/Message.js
index daadbc5c..2f1cfaf5 100644
--- a/lib/Message.js
+++ b/lib/Message.js
@@ -67,6 +67,10 @@ module.exports = class Message extends EventEmitter
     const contentType = options.contentType || 'text/plain';
 
     const requestParams = {};
+    if (options.callId !== undefined && options.callId !== null)
+    {
+      requestParams.call_id = String(options.callId);
+    }
 
     if (options.fromUserName)
     {
diff --git a/lib/Options.js b/lib/Options.js
index 86b28882..0845c561 100644
--- a/lib/Options.js
+++ b/lib/Options.js
@@ -64,6 +64,12 @@ module.exports = class Options extends EventEmitter
     const extraHeaders = Utils.cloneArray(options.extraHeaders);
     const eventHandlers = Utils.cloneObject(options.eventHandlers);
     const contentType = options.contentType || 'application/sdp';
+    const requestParams = {};
+
+    if (options.callId !== undefined && options.callId !== null)
+    {
+      requestParams.call_id = String(options.callId);
+    }
 
     // Set event handlers.
     for (const event in eventHandlers)
@@ -77,7 +83,7 @@ module.exports = class Options extends EventEmitter
     extraHeaders.push(`Content-Type: ${contentType}`);
 
     this._request = new SIPMessage.OutgoingRequest(
-      JsSIP_C.OPTIONS, target, this._ua, null, extraHeaders);
+      JsSIP_C.OPTIONS, target, this._ua, requestParams, extraHeaders);
 
     if (body)
     {
diff --git a/lib/RTCSession.js b/lib/RTCSession.js
index 762555d1..70ecd10a 100644
--- a/lib/RTCSession.js
+++ b/lib/RTCSession.js
@@ -341,6 +341,10 @@ module.exports = class RTCSession extends EventEmitter
     const anonymous = options.anonymous || false;
 
     const requestParams = { from_tag: this._from_tag };
+    if (options.callId !== undefined && options.callId !== null)
+    {
+      requestParams.call_id = String(options.callId);
+    }
 
     this._contact = this._ua.contact.toString({
       anonymous,
diff --git a/lib/Registrator.js b/lib/Registrator.js
index 89bcc3fb..9b71f256 100644
--- a/lib/Registrator.js
+++ b/lib/Registrator.js
@@ -22,7 +22,8 @@ module.exports = class Registrator
     this._expires = ua.configuration.register_expires;
 
     // Call-ID and CSeq values RFC3261 10.2.
-    this._call_id = Utils.createRandomToken(22);
+    this._call_id = this._ua.configuration.call_id ||
+      Utils.createRandomToken(22);
     this._cseq = 0;
 
     this._to_uri = ua.configuration.uri;
diff --git a/lib/UA.d.ts b/lib/UA.d.ts
index 6ee4a788..6de325db 100644
--- a/lib/UA.d.ts
+++ b/lib/UA.d.ts
@@ -17,6 +17,7 @@ export interface CallOptions extends AnswerOptions {
   anonymous?: boolean;
   fromUserName?: string;
   fromDisplayName?: string;
+  callId?: string;
 }
 
 export interface UAConfiguration {
@@ -41,6 +42,7 @@ export interface UAConfiguration {
   register?: boolean;
   register_expires?: number;
   register_from_tag_trail?: string | (() => string);
+  call_id?: string;
   registrar_server?: string;
   use_preloaded_route?: boolean;
   user_agent?: string;