diff --git a/extensions/typescript-language-features/src/utils/documentSelector.ts b/extensions/typescript-language-features/src/utils/documentSelector.ts
index 0574c3f587df550658c75e38dfc6a0812ebd48a3..780389320b8294f30a607ed34cf2b35e3bd53cc2 100644
--- a/extensions/typescript-language-features/src/utils/documentSelector.ts
+++ b/extensions/typescript-language-features/src/utils/documentSelector.ts
@@ -9,10 +9,10 @@ export interface DocumentSelector {
 	/**
 	 * Selector for files which only require a basic syntax server.
 	 */
-	readonly syntax: vscode.DocumentFilter[];
+	readonly syntax: readonly vscode.DocumentFilter[];
 
 	/**
 	 * Selector for files which require semantic server support.
 	 */
-	readonly semantic: vscode.DocumentFilter[];
+	readonly semantic: readonly vscode.DocumentFilter[];
 }
diff --git a/extensions/typescript-language-features/src/utils/fileSchemes.ts b/extensions/typescript-language-features/src/utils/fileSchemes.ts
index d465a60326e024d0825d4800961f0970a34fad80..b072923b39a9ec8e6fb630f7465bc1001ea4893f 100644
--- a/extensions/typescript-language-features/src/utils/fileSchemes.ts
+++ b/extensions/typescript-language-features/src/utils/fileSchemes.ts
@@ -13,6 +13,7 @@ export const walkThroughSnippet = 'walkThroughSnippet';
 export const semanticSupportedSchemes = [
 	file,
 	untitled,
+	walkThroughSnippet,
 ];
 
 /**