diff --git a/website/docs/language/functions/tonumber.html.md b/website/docs/language/functions/tonumber.html.md
index 1b7e0236b..3d5801255 100644
--- a/website/docs/language/functions/tonumber.html.md
+++ b/website/docs/language/functions/tonumber.html.md
@@ -14,7 +14,7 @@ Explicit type conversions are rarely necessary in Terraform because it will
 convert types automatically where required. Use the explicit type conversion
 functions only to normalize types returned in module outputs.
 
-Only numbers and strings containing decimal representations of numbers can be
+Only numbers, `null`, and strings containing decimal representations of numbers can be
 converted to number. All other values will produce an error.
 
 ## Examples
@@ -24,6 +24,8 @@ converted to number. All other values will produce an error.
 1
 > tonumber("1")
 1
+> tonumber(null)
+null
 > tonumber("no")
 Error: Invalid function argument