diff --git a/package-lock.json b/package-lock.json
index bfdf316..d6c19fb 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "json-expression-eval",
-  "version": "2.0.0",
+  "version": "2.0.1",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -1848,6 +1848,11 @@
         }
       }
     },
+    "ts-toolbelt": {
+      "version": "3.7.1",
+      "resolved": "https://registry.npmjs.org/ts-toolbelt/-/ts-toolbelt-3.7.1.tgz",
+      "integrity": "sha512-rEIk3vYCAEQ1qvCvlYjfgNdAu5BIxRIcDSgJBEDsz5UR1/oKIJz7/I8yE8x1rPqs1o2A4deCuqVvuzdMk5JxiQ=="
+    },
     "tslib": {
       "version": "1.10.0",
       "resolved": "https://registry.npmjs.org/tslib/-/tslib-1.10.0.tgz",
diff --git a/package.json b/package.json
index a69faa0..66eb958 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "json-expression-eval",
-  "version": "2.0.1",
+  "version": "2.0.2",
   "description": "evaluate a json described boolean expression using dynamic functions",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
@@ -47,5 +47,7 @@
     "tslint": "^5.18.0",
     "typescript": "^3.5.3"
   },
-  "dependencies": {}
+  "dependencies": {
+    "ts-toolbelt": "^3.7.1"
+  }
 }
diff --git a/src/index.ts b/src/index.ts
index 97cfbdf..662e02c 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,7 @@
 'use strict';
 
+import {O as tObject} from 'ts-toolbelt';
+
 export type PropertyCompareOp<C, K extends keyof C> = C[K];
 
 export type FuncCompareOp<C, F extends FunctionsTable<C>, K extends keyof F> = Parameters<F[K]>[0];
@@ -52,13 +54,7 @@ export interface NotCompareOp<C, F extends FunctionsTable<C>> {
     not: Expression<C, F>;
 }
 
-export type RequireOnlyOne<T, Keys extends keyof T = keyof T> =
-    Pick<T, Exclude<keyof T, Keys>>
-    & {
-    [K in Keys]-?:
-    Required<Pick<T, K>>
-    & Partial<Record<Exclude<Keys, K>, undefined>>
-}[Keys];
+export type RequireOnlyOne<T extends object> = tObject.Either<T, keyof T>;
 
 export type Expression<C, F extends FunctionsTable<C>> = NotCompareOp<C, F> | OrCompareOp<C, F> | AndCompareOp<C, F> |
     RequireOnlyOne<CompareOp<C, F>>;