diff --git a/extensions/json-language-features/client/src/utils/hash.ts b/extensions/json-language-features/client/src/utils/hash.ts
index 8acf7a36458efd4dd5e65cbb0157815909828dc1..dfeac828581e507c3ea815468fb6345c6d46d240 100644
--- a/extensions/json-language-features/client/src/utils/hash.ts
+++ b/extensions/json-language-features/client/src/utils/hash.ts
@@ -23,8 +23,7 @@ export function hash(obj: any, hashVal = 0): number {
 		case 'number':
 			return numberHash(obj, hashVal);
 		case 'undefined':
-			// TODO: TS 3.1 upgrade. Why are we passing undefined here?
-			return numberHash(obj as any, 937);
+			return 937 * 31;
 		default:
 			return numberHash(obj, 617);
 	}