diff --git a/ch07-prediction/feature_creation.R b/ch07-prediction/feature_creation.R
index 34bc339..1825919 100644
--- a/ch07-prediction/feature_creation.R
+++ b/ch07-prediction/feature_creation.R
@@ -70,6 +70,7 @@ session_based_features <- function(events_data, current_week) {
   events_data |>
     filter(week <= current_week) |>
     distinct(user, session_id, session_len) |>
+    filter(session_len > 0) |>
     group_by(user) |>
     mutate(session_cnt = n(),
            avg_session_len = median(session_len),