diff --git a/package-lock.json b/package-lock.json
index c97dd04..d14c150 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@vacasaoss/ts-force-project",
-  "version": "3.4.4",
+  "version": "4.0.0",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
       "name": "@vacasaoss/ts-force-project",
-      "version": "3.4.4",
+      "version": "4.0.0",
       "hasInstallScript": true,
       "license": "ISC"
     }
diff --git a/package.json b/package.json
index e4b87ed..adf1635 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@vacasaoss/ts-force-project",
-  "version": "3.4.4",
+  "version": "4.0.0",
   "description": "",
   "scripts": {
     "postinstall": "cd ts-force && npm install && npm run build && cd ../ts-force-gen && npm install",
@@ -25,4 +25,4 @@
     "url": "https://github.com/ChuckJonas/ts-force/issues"
   },
   "homepage": "https://github.com/ChuckJonas/ts-force#readme"
-}
\ No newline at end of file
+}
diff --git a/ts-force-gen/package-lock.json b/ts-force-gen/package-lock.json
index b73f5cf..f01c877 100644
--- a/ts-force-gen/package-lock.json
+++ b/ts-force-gen/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@vacasaoss/ts-force-gen",
-  "version": "3.4.4",
+  "version": "4.0.0",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
       "name": "@vacasaoss/ts-force-gen",
-      "version": "3.4.4",
+      "version": "4.0.0",
       "license": "BSD-3-Clause",
       "dependencies": {
         "@salesforce/core": "^2.12.3",
diff --git a/ts-force-gen/package.json b/ts-force-gen/package.json
index c0cd74c..9c379cc 100644
--- a/ts-force-gen/package.json
+++ b/ts-force-gen/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@vacasaoss/ts-force-gen",
-  "version": "3.4.4",
+  "version": "4.0.0",
   "description": "Code generation for ts-force",
   "main": "build/index.js",
   "typings": "build/index.d.ts",
@@ -63,4 +63,4 @@
     "ts-morph": "^2.1.0",
     "tslib": "^2.0.3"
   }
-}
\ No newline at end of file
+}
diff --git a/ts-force/package-lock.json b/ts-force/package-lock.json
index 5a6ec6c..979260e 100644
--- a/ts-force/package-lock.json
+++ b/ts-force/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@vacasaoss/ts-force",
-  "version": "3.4.4",
+  "version": "4.0.0",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
       "name": "@vacasaoss/ts-force",
-      "version": "3.4.4",
+      "version": "4.0.0",
       "license": "BSD-3-Clause",
       "dependencies": {
         "@types/cometd": "^4.0.4",
diff --git a/ts-force/package.json b/ts-force/package.json
index d599107..c034952 100644
--- a/ts-force/package.json
+++ b/ts-force/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@vacasaoss/ts-force",
-  "version": "3.4.4",
+  "version": "4.0.0",
   "description": "a typescript client for connecting with salesforce APIs",
   "main": "build/index.js",
   "typings": "build/index.d.ts",
@@ -57,4 +57,4 @@
     "reflect-metadata": "^0.1.10",
     "tslib": "^1.6.0"
   }
-}
\ No newline at end of file
+}
diff --git a/ts-force/src/rest/restHeader.ts b/ts-force/src/rest/restHeader.ts
new file mode 100644
index 0000000..8beebf4
--- /dev/null
+++ b/ts-force/src/rest/restHeader.ts
@@ -0,0 +1,8 @@
+export type RequestHeadersInput = {
+  'Sforce-Auto-Assign'?: boolean;
+  'If-Modified-Since'?: Date;
+  'If-Unmodified-Since'?: Date;
+};
+export type GeneralRequestHeadersInput = RequestHeadersInput | Record<string, string>;
+
+export const ConditionalRequestHeaders = ['If-Match', 'If-None-Match', 'If-Modified-Since', 'If-Unmodified-Since'];
diff --git a/ts-force/src/rest/restObject.ts b/ts-force/src/rest/restObject.ts
index f729ff4..f30607b 100644
--- a/ts-force/src/rest/restObject.ts
+++ b/ts-force/src/rest/restObject.ts
@@ -10,11 +10,10 @@ import {
 import { Rest } from './rest';
 import { getSFieldProps, SalesforceFieldType, SFieldProperties } from './sObjectDecorators';
 import { SObject } from './sObject';
-import { CompositeError, StandardRestError } from './errors';
+import { CompositeError, ConditionalError, StandardRestError } from './errors';
 import { FieldProps } from '..';
 import { CalendarDate, calendarToString, getCalendarDate } from '../utils/calendarDate';
-import { AxiosRequestHeaders, AxiosResponse } from 'axios';
-import { STATUS_CODES } from 'http';
+import { ConditionalRequestHeaders, GeneralRequestHeadersInput } from './restHeader';
 
 export interface DMLResponse {
   id: string;
@@ -229,12 +228,7 @@ export abstract class RestObject extends SObject {
    * @returns {Promise<void>}
    * @memberof RestObject
    */
-  public async update(opts?: { 
-      refresh?: boolean; 
-      sendAllFields?: boolean;
-      ifModifiedSince?: Date;
-      ifUnmodifiedSince?: Date;
-     }): Promise<this> {
+  public async update(opts?: { refresh?: boolean; sendAllFields?: boolean; headers?: GeneralRequestHeadersInput }): Promise<this> {
     opts = opts || {};
     if (this.id == null) {
       throw new Error('Must have Id to update!');
@@ -242,14 +236,22 @@ export abstract class RestObject extends SObject {
     if (opts.refresh === true) {
       return this.updateComposite(opts.sendAllFields);
     } else {
-      const headers = {};
-      if (opts.ifModifiedSince) headers['If-Modified-Since'] = opts.ifModifiedSince.toUTCString()
-      if (opts.ifUnmodifiedSince) headers['If-Unmodified-Since'] = opts.ifUnmodifiedSince.toUTCString()
+      const headers = this.convertValuesToStrings(opts.headers);
       const response = await this._client.request.patch(
         `${this.attributes.url}/${this.id}`,
         this.toJson({ dmlMode: opts.sendAllFields ? 'update' : 'update_modified_only' }),
         { headers }
       );
+
+      // Check if it contains Conditional Request Headers and deal with errors
+      const containsConditionalHeader = Object.keys(headers).some((key) => ConditionalRequestHeaders.includes(key));
+      if (containsConditionalHeader && (response.status === 304 || response.status === 412)) {
+        const problematicHeaders = Object.keys(headers)
+          .filter((key) => ConditionalRequestHeaders.includes(key))
+          .join(', ');
+        throw new ConditionalError(`Conditions not met. Headers: ${problematicHeaders}`);
+      }
+
       this._modified.clear();
     }
     return this;
@@ -497,4 +499,18 @@ export abstract class RestObject extends SObject {
       throw e;
     }
   }
+
+  private convertValuesToStrings(headerInput: GeneralRequestHeadersInput) {
+    const headers = {};
+    for (const key in headerInput) {
+      const value = headerInput[key];
+      if (value instanceof Date) {
+        headerInput[key] = (value as Date).toUTCString();
+      } else if (typeof value === 'boolean') {
+        headerInput[key] = value.toString();
+      }
+      headers[key] = headerInput[key];
+    }
+    return headers;
+  }
 }
diff --git a/ts-force/src/test/rest/restObjects.spec.ts b/ts-force/src/test/rest/restObjects.spec.ts
index 7e7c667..6ddd330 100644
--- a/ts-force/src/test/rest/restObjects.spec.ts
+++ b/ts-force/src/test/rest/restObjects.spec.ts
@@ -175,7 +175,7 @@ describe('Generated Classes', () => {
     await acc.delete();
   })  
   
-  it('handle ifModifiedSince', async () => {
+  it('handle multiple headers', async () => {
     const modifiedDate = new Date();
     let acc = new Account({
       name: 'account'
@@ -183,29 +183,20 @@ describe('Generated Classes', () => {
     await acc.insert();
     //@ts-expect-error
     acc._client.request.interceptors.request.use((config) => {
-      if (config.method === 'patch')
-        expect(config.headers["If-Modified-Since"]).to.equal(modifiedDate.toUTCString());
+      if (config.method === 'patch') expect(config.headers['Sforce-Auto-Assign']).to.equal('true');
+      if (config.method === 'patch') expect(config.headers['Sforce-Mru']).to.equal('updateMru=true');
+      if (config.method === 'patch') expect(config.headers['If-Modified-Since']).to.equal(new Date().toUTCString());
       return config
     });
     acc.name = "account2";
-    await acc.update({ refresh: false, ifModifiedSince: new Date()});
-    await acc.delete();
-  })
-
-  it('handle ifUmodifiedSince', async () => {
-    const modifiedDate = new Date();
-    let acc = new Account({
-      name: 'account'
+    await acc.update({
+      refresh: false,
+      headers: {
+        'Sforce-Auto-Assign': true,
+        'If-Modified-Since': new Date(),
+        'Sforce-Mru': 'updateMru=true',
+      },
     });
-    await acc.insert();
-    //@ts-expect-error
-    acc._client.request.interceptors.request.use((config) => {
-      if (config.method === 'patch')
-        expect(config.headers["If-Unmodified-Since"]).to.equal(modifiedDate.toUTCString());
-      return config
-    });
-    acc.name = "account2";
-    await acc.update({ refresh: false, ifUnmodifiedSince: new Date()});
     await acc.delete();
   })
 
@@ -489,4 +480,4 @@ describe('Generated Classes', () => {
     await c.delete();
   });
 
-});
+});
\ No newline at end of file