diff --git a/challenges/01-front-end-development-certification/basic-bonfires.json b/challenges/01-front-end-development-certification/basic-bonfires.json
index cdc794edaa..c8ed5e6c3a 100644
--- a/challenges/01-front-end-development-certification/basic-bonfires.json
+++ b/challenges/01-front-end-development-certification/basic-bonfires.json
@@ -124,6 +124,7 @@
         "If the integer is represented with the letter n, a factorial is the product of all positive integers less than or equal to n.",
         "Factorials are often represented with the shorthand notation <code>n!</code>",
         "For example: <code>5! = 1 * 2 * 3 * 4 * 5 = 120</code>",
+        "Only integers greater than or equal to zero will be supplied to the function.",
         "Remember to use <a href=\"http://forum.freecodecamp.com/t/how-to-get-help-when-you-are-stuck/19514\" target=\"_blank\">Read-Search-Ask</a> if you get stuck. Write your own code."
       ],
       "challengeSeed": [