diff --git a/packages/shared/src/is.ts b/packages/shared/src/is.ts
index 347da6e1af3..a3d9f26454d 100644
--- a/packages/shared/src/is.ts
+++ b/packages/shared/src/is.ts
@@ -27,8 +27,8 @@ export function isNumber (o: unknown): o is number {
   return typeof o === 'number'
 }
 
-export function isBooleanStringLiteral (o: unknown): o is string {
-  return o === 'true' || o === 'false'
+export function isBooleanStringLiteral (o: unknown): o is boolean {
+  return o === 'true' || o === 'false' || o === '!0' || o === '!1'
 }
 
 export function isObjectStringLiteral (o: unknown): o is string {