diff --git a/src/koans/04_sets.clj b/src/koans/04_sets.clj
index 0b5d14e..d6b4063 100644
--- a/src/koans/04_sets.clj
+++ b/src/koans/04_sets.clj
@@ -1,5 +1,6 @@
 (ns koans.04-sets
-  (:require [koan-engine.core :refer :all]))
+  (:require [koan-engine.core :refer :all]
+            [clojure.set :as set]))
 
 (meditations
   "You can create a set by converting another collection"
@@ -12,10 +13,10 @@
   (= __ (set '(1 1 2 2 3 3 4 4 5 5)))
 
   "You can ask clojure for the union of two sets"
-  (= __ (clojure.set/union #{1 2 3 4} #{2 3 5}))
+  (= __ (set/union #{1 2 3 4} #{2 3 5}))
 
   "And also the intersection"
-  (= __ (clojure.set/intersection #{1 2 3 4} #{2 3 5}))
+  (= __ (set/intersection #{1 2 3 4} #{2 3 5}))
 
   "But don't forget about the difference"
-  (= __ (clojure.set/difference #{1 2 3 4 5} #{2 3 5})))
+  (= __ (set/difference #{1 2 3 4 5} #{2 3 5})))
diff --git a/src/koans/21_group_by.clj b/src/koans/21_group_by.clj
index 1e845d5..e7a0408 100644
--- a/src/koans/21_group_by.clj
+++ b/src/koans/21_group_by.clj
@@ -19,20 +19,20 @@
   "You can also group by a primary key"
   (= __
      (group-by :id [{:id 1 :name "Bob"}
-                    {:id 2 :name "Mike"}
+                    {:id 2 :name "Jennifer"}
                     {:id 1 :last-name "Smith"} ]))
 
   "But be careful when you group by non-required key"
   (= {"Bob" [{:name "Bob" :id 1}]
-      "Mike" [{:name "Mike" :id 2}]
+      "Jennifer" [{:name "Jennifer" :id 2}]
       __ [{:last-name "Smith" :id 1}]}
    (group-by :name [{:id 1 :name "Bob"}
-                    {:id 2 :name "Mike"}
+                    {:id 2 :name "Jennifer"}
                     {:id 1 :last-name "Smith"}]))
 
   "The true power of group-by comes with custom functions"
   (= __
      (group-by #(if (:bad %) :naughty-list :nice-list)
                [{:name "Jimmy" :bad true}
-                {:name "Jack" :bad false}
+                {:name "Anna" :bad false}
                 {:name "Joe" :bad true}])))