diff --git a/src/index.ts b/src/index.ts
index 2f44d8e..e067960 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -208,7 +208,14 @@ const jsonToCss = function (_css, className = "", refresh = () => { }) {
   }
 }
 
-const CSS = function (rules, name = 'class') {
+const CSS = function (rules, name = 'class') : {
+  getStyle(): string;
+  inject(): void;
+  remove(callbackOnFirstSwap?: () => void): boolean;
+  refresh(): any;
+  toString(): string;
+  inherit(): any;
+} | string {
   let className = name + randomId();
   let temp = '';
 
diff --git a/tests/index.spec.js b/tests/index.spec.js
index 44c62cc..6888d94 100644
--- a/tests/index.spec.js
+++ b/tests/index.spec.js
@@ -108,6 +108,8 @@ describe('', () => {
       for (let unit in units) {
         if (unit === 'pct') {
           expect(units[unit](1)).toBe('1%');
+        } else if (unit === 'inch') {
+          expect(units[unit](1)).toBe('1in');
         } else {
           expect(units[unit](1)).toBe('1' + unit);
         }