diff --git a/ch5/ch5-06.md b/ch5/ch5-06.md
index 9be5819..d59bd38 100644
--- a/ch5/ch5-06.md
+++ b/ch5/ch5-06.md
@@ -83,7 +83,7 @@ func topoSort(m map[string][]string) []string {
 	}
 	var keys []string
 	for key := range m {
-	keys = append(keys, key)
+		keys = append(keys, key)
 	}
 	sort.Strings(keys)
 	visitAll(keys)