diff --git a/package-lock.json b/package-lock.json
index b455df3..a5917e3 100755
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "spring-filter-query-builder",
-  "version": "1.0.0",
+  "version": "1.0.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "spring-filter-query-builder",
-      "version": "1.0.0",
+      "version": "1.0.1",
       "hasInstallScript": true,
       "license": "MIT",
       "devDependencies": {
diff --git a/package.json b/package.json
index abbc26b..aad3c3e 100755
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "spring-filter-query-builder",
-  "version": "1.0.0",
+  "version": "1.0.1",
   "description": "",
   "main": "dist/cjs/index.js",
   "module": "dist/esm/index.js",
diff --git a/src/operators.ts b/src/operators.ts
index 874cc63..2ad8f7b 100755
--- a/src/operators.ts
+++ b/src/operators.ts
@@ -26,7 +26,10 @@ export class Not extends Operator {
   }
 
   public toString(): string {
-    return `${this.operatorKeyWord} ${this.items[0].toString()}`;
+    if (this.items[0] instanceof Operator) {
+      return `${this.operatorKeyWord}${this.items[0].toString()}`;
+    }
+    return `${this.operatorKeyWord}(${this.items[0].toString()})`;
   }
 }
 
diff --git a/test/operators.test.ts b/test/operators.test.ts
index d953931..4bf4298 100644
--- a/test/operators.test.ts
+++ b/test/operators.test.ts
@@ -9,5 +9,9 @@ test('or', () => {
 });
 
 test('not', () => {
-  expect(sfNot(sfOr([sfGt('id', 100), sfIsNull('category.order')])).toString()).toBe('not (id > 100 or category.order is null)');
+  expect(sfNot(sfOr([sfGt('id', 100), sfIsNull('category.order')])).toString()).toBe('not(id > 100 or category.order is null)');
+});
+
+test('not', () => {
+  expect(sfNot(sfGt('id', 100)).toString()).toBe('not(id > 100)');
 });