diff --git a/calculator/calculator.spec.js b/calculator/calculator.spec.js
index 29b90af..a8b5564 100644
--- a/calculator/calculator.spec.js
+++ b/calculator/calculator.spec.js
@@ -56,7 +56,7 @@ describe('power', function() {
 
 describe('factorial', function() {
 	it('computes the factorial of 0', function() {
-		expect(calculator.factorial(0)).toEqual(0);
+		expect(calculator.factorial(0)).toEqual(1); // 0! = 1
 	});
 
 	it('computes the factorial of 1', function() {
@@ -74,4 +74,4 @@ describe('factorial', function() {
 	it('computes the factorial of 10', function() {
 		expect(calculator.factorial(10)).toEqual(3628800);
 	});
-});
\ No newline at end of file
+});