diff --git a/strings.Rmd b/strings.Rmd
index 86de4b5..84c697e 100644
--- a/strings.Rmd
+++ b/strings.Rmd
@@ -612,7 +612,7 @@ str_view_all("abababa", "aba")
 
 Note the use of `str_view_all()`. As you'll shortly learn, many stringr functions come in pairs: one function works with a single match, and the other works with all matches. The second function will have the suffix `_all`.
 
-### Exercises
+#### Exercises
 
 1.  For each of the following challenges, try solving it by using both a single
     regular expression, and a combination of multiple `str_detect()` calls.