diff --git a/session_5/session_5.Rmd b/session_5/session_5.Rmd
index 63f99d39c544ceceb4324ed3c9b26b85dc17708b..16aed13072f41788ee217e7c9e3e7a7efc09611d 100644
--- a/session_5/session_5.Rmd
+++ b/session_5/session_5.Rmd
@@ -281,7 +281,7 @@ flights %>%
   ) %>% 
   mutate(wday = strftime(time_hour,'%A')) %>% 
   group_by(wday) %>% 
-  mutate(
+  summarise(
     prop_cancel_day = sum(canceled)/n(),
     av_delay = mean(dep_delay, na.rm = TRUE)
   ) %>%