diff --git a/functions.qmd b/functions.qmd
index 1b05e1d..7b32844 100644
--- a/functions.qmd
+++ b/functions.qmd
@@ -72,7 +72,7 @@ df |> mutate(
 You might be able to puzzle out that this rescales each column to have a range from 0 to 1.
 But did you spot the mistake?
 When Hadley wrote this code he made an error when copying-and-pasting and forgot to change an `a` to a `b`.
-Preventing this type of mistake of is one very good reason to learn how to write functions.
+Preventing this type of mistake is one very good reason to learn how to write functions.
 
 ### Writing a function