diff --git a/src/malli/transform.cljc b/src/malli/transform.cljc
index 3381f0924..6fcbf5008 100644
--- a/src/malli/transform.cljc
+++ b/src/malli/transform.cljc
@@ -164,6 +164,14 @@
 (defn -transform-map-keys [f]
   #(cond->> % (map? %) (into {} (map (fn [[k v]] [(f k) v])))))
 
+(defn -transform-if-valid [f schema]
+  (let [validator (m/-validator schema)]
+    (fn [x]
+      (let [out (f x)]
+        (if (validator out)
+          out
+          x)))))
+
 ;;
 ;; sequential
 ;;
@@ -354,9 +362,13 @@
     {:name :json
      :decoders (-> (-json-decoders)
                    (assoc :map-of {:compile (fn [schema _]
-                                              (or (some-> schema (m/children) (first) (m/type) map-of-key-decoders
-                                                          (m/-comp m/-keyword->string) (-transform-map-keys))
-                                                  (-transform-map-keys m/-keyword->string)))})
+                                              (let [key-schema (some-> schema (m/children) (first))]
+                                                (or (some-> key-schema (m/type) map-of-key-decoders
+                                                            (-interceptor schema {}) m/-intercepting
+                                                            (m/-comp m/-keyword->string)
+                                                            (-transform-if-valid key-schema)
+                                                            (-transform-map-keys))
+                                                    (-transform-map-keys m/-keyword->string))))})
                    (cond-> json-vectors (assoc :vector -sequential->vector)))
      :encoders (-json-encoders)})))
 
diff --git a/test/malli/transform_test.cljc b/test/malli/transform_test.cljc
index c8f86775e..f2509ec99 100644
--- a/test/malli/transform_test.cljc
+++ b/test/malli/transform_test.cljc
@@ -230,6 +230,9 @@
   (testing "map-of"
     (is (= {1 :abba, 2 :jabba} (m/decode [:map-of int? keyword?] {"1" "abba", "2" "jabba"} mt/string-transformer)))
     (is (= {1 :abba, 2 :jabba} (m/decode [:map-of int? keyword?] {"1" "abba", "2" "jabba"} mt/json-transformer)))
+    (testing "keeps original value if decoding fails"
+      (is (= {1 :abba, :xyz :jabba} (m/decode [:map-of int? keyword?] {"1" "abba", :xyz "jabba"} mt/json-transformer)))
+      (is (= {1 :abba, :xyz :jabba} (m/decode [:map-of int? keyword?] {"1" "abba", :xyz "jabba"} mt/json-transformer))))
     (is (= nil (m/decode [:map-of int? keyword?] nil mt/string-transformer)))
     (is (= ::invalid (m/decode [:map-of int? keyword?] ::invalid mt/json-transformer))))
 
@@ -348,6 +351,18 @@
         [:repeat {:min 2, :max 4} int?] [1 :kikka] [1 :kikka]
         [:repeat {:min 2, :max 4} int?] [1 2 3 4 5] [1 2 3 4 5]))))
 
+(deftest map-of-enum-transform-test-819
+  (let [schema [:map-of
+                [:enum {:encode/json name
+                        :decode/json keyword}
+                 :a :b :c]
+                int?]
+        m {:a 1 :b 2}
+        encoded (m/encode schema m mt/json-transformer)
+        decoded (m/decode schema encoded mt/json-transformer)]
+    (is (= {"a" 1 "b" 2} encoded))
+    (is (= m decoded))))
+
 (deftest collection-transform-test
   (testing "decode"
     (is (= #{1 2 3} (m/decode [:set int?] [1 2 3] mt/collection-transformer)))
@@ -879,11 +894,11 @@
                   {"0" "2ac307dc-4ec8-4046-9b7e-57716b7ecfd2"
                    "1" "820e5003-6fff-480b-9e2b-ec3cdc5d2f78"
                    "2" "017de28f-5801-8c62-9ce9-cef70883794a"}]]
-
-      (is (= {0 #uuid"2ac307dc-4ec8-4046-9b7e-57716b7ecfd2"
-              1 #uuid"820e5003-6fff-480b-9e2b-ec3cdc5d2f78"
-              2 #uuid"017de28f-5801-8c62-9ce9-cef70883794a"}
-             (m/decode schema data mt/json-transformer))))))
+      (testing data
+        (is (= {0 #uuid"2ac307dc-4ec8-4046-9b7e-57716b7ecfd2"
+                1 #uuid"820e5003-6fff-480b-9e2b-ec3cdc5d2f78"
+                2 #uuid"017de28f-5801-8c62-9ce9-cef70883794a"}
+               (m/decode schema data mt/json-transformer)))))))
 
 #?(:clj
    (deftest -safe-test