diff --git a/src/headless/public/Terminal.test.ts b/src/headless/public/Terminal.test.ts
index 7f341b911c..43aaf62860 100644
--- a/src/headless/public/Terminal.test.ts
+++ b/src/headless/public/Terminal.test.ts
@@ -125,13 +125,10 @@ describe('Headless API Tests', function (): void {
     });
     it('get options', () => {
       const options: ITerminalOptions = term.options;
-      strictEqual(options.cols, 80);
-      strictEqual(options.rows, 24);
+      strictEqual(options.lineHeight, 1);
+      strictEqual(options.cursorWidth, 1);
     });
     it('set options', async () => {
-      const options: ITerminalOptions = term.options;
-      throws(() => options.cols = 40);
-      throws(() => options.rows = 20);
       term.options.scrollback = 1;
       strictEqual(term.options.scrollback, 1);
       term.options= {
diff --git a/src/headless/public/Terminal.ts b/src/headless/public/Terminal.ts
index 451d2372ad..efc0a8a165 100644
--- a/src/headless/public/Terminal.ts
+++ b/src/headless/public/Terminal.ts
@@ -7,11 +7,10 @@ import { IEvent } from 'common/EventEmitter';
 import { BufferNamespaceApi } from 'common/public/BufferNamespaceApi';
 import { ParserApi } from 'common/public/ParserApi';
 import { UnicodeApi } from 'common/public/UnicodeApi';
-import { IBufferNamespace as IBufferNamespaceApi, IMarker, IModes, IParser, ITerminalAddon, IUnicodeHandling, Terminal as ITerminalApi } from 'xterm-headless';
+import { IBufferNamespace as IBufferNamespaceApi, IMarker, IModes, IParser, ITerminalAddon, ITerminalInitOnlyOptions, IUnicodeHandling, Terminal as ITerminalApi } from 'xterm-headless';
 import { Terminal as TerminalCore } from 'headless/Terminal';
 import { AddonManager } from 'common/public/AddonManager';
 import { ITerminalOptions } from 'common/Types';
-
 /**
  * The set of options that only have an effect when set in the Terminal constructor.
  */
@@ -24,7 +23,7 @@ export class Terminal implements ITerminalApi {
   private _buffer: BufferNamespaceApi | undefined;
   private _publicOptions: ITerminalOptions;
 
-  constructor(options?: ITerminalOptions) {
+  constructor(options?: ITerminalOptions & ITerminalInitOnlyOptions) {
     this._core = new TerminalCore(options);
     this._addonManager = new AddonManager();
 
diff --git a/typings/xterm-headless.d.ts b/typings/xterm-headless.d.ts
index d39a709862..cda7ad1a50 100644
--- a/typings/xterm-headless.d.ts
+++ b/typings/xterm-headless.d.ts
@@ -14,7 +14,7 @@ declare module 'xterm-headless' {
   export type LogLevel = 'debug' | 'info' | 'warn' | 'error' | 'off';
 
   /**
-   * An object containing start up options for the terminal.
+   * An object containing options for the terminal.
    */
   export interface ITerminalOptions {
     /**
@@ -48,11 +48,6 @@ declare module 'xterm-headless' {
      */
     convertEol?: boolean;
 
-    /**
-     * The number of columns in the terminal.
-     */
-    cols?: number;
-
     /**
      * Whether the cursor blinks.
      */
@@ -145,11 +140,6 @@ declare module 'xterm-headless' {
      */
     rightClickSelectsWord?: boolean;
 
-    /**
-     * The number of rows in the terminal.
-     */
-    rows?: number;
-
     /**
      * Whether screen reader support is enabled. When on this will expose
      * supporting elements in the DOM to support NVDA on Windows and VoiceOver
@@ -210,6 +200,22 @@ declare module 'xterm-headless' {
     windowOptions?: IWindowOptions;
   }
 
+  /**
+   * An object containing additional options for the terminal that can only be
+   * set on start up.
+   */
+  export interface ITerminalInitOnlyOptions {
+    /**
+     * The number of columns in the terminal.
+     */
+    cols?: number;
+
+    /**
+     * The number of rows in the terminal.
+     */
+    rows?: number;
+  }
+
   /**
    * Contains colors to theme the terminal with.
    */
@@ -558,7 +564,7 @@ declare module 'xterm-headless' {
      *
      * @param options An object containing a set of options.
      */
-    constructor(options?: ITerminalOptions);
+    constructor(options?: ITerminalOptions & ITerminalInitOnlyOptions);
 
     /**
      * Adds an event listener for when the bell is triggered.