diff --git a/src/vs/vscode.d.ts b/src/vs/vscode.d.ts
index 7064bbcd593..46fac88b39f 100644
--- a/src/vs/vscode.d.ts
+++ b/src/vs/vscode.d.ts
@@ -2569,8 +2569,8 @@ declare module 'vscode' {
 	 * The MarkdownString represents human-readable text that supports formatting via the
 	 * markdown syntax. Standard markdown is supported, also tables, but no embedded html.
 	 *
-	 * When created with `supportThemeIcons` then rendering of {@link ThemeIcon theme icons} via
-	 * the `$(<name>)`-syntax is supported.
+	 * Rendering of {@link ThemeIcon theme icons} via the `$(<name>)`-syntax is supported
+	 * when the {@link MarkdownString.supportThemeIcons `supportThemeIcons`} is set to `true`.
 	 */
 	export class MarkdownString {
 
@@ -2588,7 +2588,7 @@ declare module 'vscode' {
 		/**
 		 * Indicates that this markdown string can contain {@link ThemeIcon ThemeIcons}, e.g. `$(zap)`.
 		 */
-		readonly supportThemeIcons?: boolean;
+		supportThemeIcons?: boolean;
 
 		/**
 		 * Creates a new markdown string with the given value.
diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index 54ba8c1e240..cff5b2a56c9 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -1332,6 +1332,10 @@ export class MarkdownString implements vscode.MarkdownString {
 		return this.#delegate.supportThemeIcons;
 	}
 
+	set supportThemeIcons(value: boolean | undefined) {
+		this.#delegate.supportThemeIcons = value;
+	}
+
 	appendText(value: string): vscode.MarkdownString {
 		this.#delegate.appendText(value);
 		return this;