diff --git a/README.md b/README.md
index af82b8f36..0d015fbee 100644
--- a/README.md
+++ b/README.md
@@ -891,9 +891,12 @@ const isEven = num => num % 2 === 0;
 Use recursion.
 If `n` is less than or equal to `1`, return `1`.
 Otherwise, return the product of `n` and the factorial of `n - 1`.
+Throws an exception if `n` is a negative number.
 
 ```js
-const factorial = n => n <= 1 ? 1 : n * factorial(n - 1);
+const factorial = n =>
+  n < 0 ? (() => { throw new TypeError('Negative numbers are not allowed!') })()
+  : n <= 1 ? 1 : n * factorial(n - 1);
 // factorial(6) -> 720
 ```
 
diff --git a/snippets/factorial.md b/snippets/factorial.md
index 155b7229e..d881fe941 100644
--- a/snippets/factorial.md
+++ b/snippets/factorial.md
@@ -3,8 +3,11 @@
 Use recursion.
 If `n` is less than or equal to `1`, return `1`.
 Otherwise, return the product of `n` and the factorial of `n - 1`.
+Throws an exception if `n` is a negative number.
 
 ```js
-const factorial = n => n <= 1 ? 1 : n * factorial(n - 1);
+const factorial = n =>
+  n < 0 ? (() => { throw new TypeError('Negative numbers are not allowed!') })()
+  : n <= 1 ? 1 : n * factorial(n - 1);
 // factorial(6) -> 720
 ```