diff --git a/src/sci/impl/analyzer.cljc b/src/sci/impl/analyzer.cljc
index 13148810..50da1725 100644
--- a/src/sci/impl/analyzer.cljc
+++ b/src/sci/impl/analyzer.cljc
@@ -1698,7 +1698,14 @@
 
 (defn map-fn [children-count]
   (if (<= children-count 16)
-    array-map hash-map))
+    #?(:clj #(let [^objects arr (into-array %&)]
+               (clojure.lang.PersistentArrayMap/createWithCheck arr))
+       :cljs #(PersistentArrayMap.createWithCheck (into-array %&))
+       :default array-map)
+    #?(:clj #(let [^objects arr (into-array %&)]
+               (clojure.lang.PersistentHashMap/createWithCheck arr))
+       :cljs #(PersistentHashMap.createWithCheck (into-array %&))
+       :default hash-map)))
 
 (defn return-map [ctx the-map analyzed-children]
   (let [mf (map-fn (count analyzed-children))]
diff --git a/test/sci/core_test.cljc b/test/sci/core_test.cljc
index 6553321d..5303d01a 100644
--- a/test/sci/core_test.cljc
+++ b/test/sci/core_test.cljc
@@ -110,7 +110,8 @@
                       :d #{*in* (inc *in*)}
                       :e {:a *in*}}))))
   (testing "duplicate keys"
-    (is (thrown-with-msg? Exception #"Duplicate key" (sci/eval-string "(let [a 1 b 1] #{a b})"))))
+    (is (thrown-with-msg? Exception #"Duplicate key" (sci/eval-string "(let [a 1 b 1] #{a b})")))
+    (is (thrown-with-msg? Exception #"Duplicate key" (sci/eval-string "(let [a 1 b 1] {a 1 b 2})"))))
   (testing "quoting"
     (is (= {:a '*in*} (eval* 1 (str "'{:a *in*}"))))
     (is (= '#{1 2 3 *in*} (eval* 4 "'#{1 2 3 *in*}")))