diff --git a/src/ring/middleware/json.clj b/src/ring/middleware/json.clj
index e89daf6..6f2d3a2 100644
--- a/src/ring/middleware/json.clj
+++ b/src/ring/middleware/json.clj
@@ -13,7 +13,7 @@
   (if-let [type (get-in request [:headers "content-type"])]
     (not (empty? (re-find #"^application/(.+\+)?json" type)))))
 
-(defn- read-json [request & [{:keys [keywords? bigdecimals?]}]]
+(defn- read-json [request & [{:keys [keywords? bigdecimals? key-fn]}]]
   (if (json-request? request)
     (if-let [^InputStream body (:body request)]
       (let [^String encoding (or (character-encoding request)
@@ -21,7 +21,7 @@
             body-reader (java.io.InputStreamReader. body encoding)]
         (binding [parse/*use-bigdecimals?* bigdecimals?]
           (try
-            [true (json/parse-stream body-reader keywords?)]
+            [true (json/parse-stream body-reader (or key-fn keywords?))]
             (catch com.fasterxml.jackson.core.JsonParseException ex
               [false nil])))))))
 
@@ -34,8 +34,8 @@
 (defn json-body-request
   "Parse a JSON request body and assoc it back into the :body key. Returns nil
   if the JSON is malformed. See: wrap-json-body."
-  [request {:keys [keywords? bigdecimals?]}]
-  (if-let [[valid? json] (read-json request {:keywords? keywords? :bigdecimals? bigdecimals?})]
+  [request options]
+  (if-let [[valid? json] (read-json request options)]
     (if valid? (assoc request :body json))
     request))
 
@@ -46,6 +46,7 @@
 
   Accepts the following options:
 
+  :key-fn             - function that will be applied to each key
   :keywords?          - true if the keys of maps should be turned into keywords
   :bigdecimals?       - true if BigDecimals should be used instead of Doubles
   :malformed-response - a response map to return when the JSON is malformed"
@@ -74,8 +75,8 @@
   "Parse the body of JSON requests into a map of parameters, which are added
   to the request map on the :json-params and :params keys. Returns nil if the
   JSON is malformed. See: wrap-json-params."
-  [request {:keys [bigdecimals?]}]
-  (if-let [[valid? json] (read-json request {:bigdecimals? bigdecimals?})]
+  [request options]
+  (if-let [[valid? json] (read-json request options)]
     (if valid? (assoc-json-params request json))
     request))
 
@@ -85,6 +86,7 @@
 
   Accepts the following options:
 
+  :key-fn             - function that will be applied to each key
   :bigdecimals?       - true if BigDecimals should be used instead of Doubles
   :malformed-response - a response map to return when the JSON is malformed
 
@@ -130,6 +132,7 @@
 
   Accepts the following options:
 
+  :key-fn            - function that will be applied to each key
   :pretty            - true if the JSON should be pretty-printed
   :escape-non-ascii  - true if non-ASCII characters should be escaped with \\u
   :stream?           - true to create JSON body as stream rather than string"
diff --git a/test/ring/middleware/test/json.clj b/test/ring/middleware/test/json.clj
index 80c9dc4..b5490a3 100644
--- a/test/ring/middleware/test/json.clj
+++ b/test/ring/middleware/test/json.clj
@@ -17,7 +17,7 @@
                       :body (string-input-stream "{\"foo\": \"bar\"}")}
             response (handler request)]
         (is (= {"foo" "bar"} (:body response)))))
-    
+
     (testing "custom json body"
       (let [request  {:headers {"content-type" "application/vnd.foobar+json; charset=UTF-8"}
                       :body (string-input-stream "{\"foo\": \"bar\"}")}
@@ -45,6 +45,13 @@
             response (handler request)]
         (is (= {"foo" "你好"} (:body response))))))
 
+  (let [handler (wrap-json-body identity {:key-fn (fn [k] (.toUpperCase (name k)))})]
+    (testing "key-fn"
+      (let [request  {:headers {"content-type" "application/json; charset=UTF-8"}
+                      :body (string-input-stream "{\"foo\": \"bar\"}")}
+            response (handler request)]
+        (is (= {"FOO" "bar"} (:body response))))))
+
   (let [handler (wrap-json-body identity {:keywords? true})]
     (testing "keyword keys"
       (let [request  {:headers {"content-type" "application/json"}
@@ -146,7 +153,7 @@
           (is (= (get-in @response [:body :bigdecimals]) true)))))))
 
 (deftest test-json-params
-  (let [handler  (wrap-json-params identity)]
+  (let [handler (wrap-json-params identity)]
     (testing "xml body"
       (let [request  {:headers {"content-type" "application/xml"}
                       :body (string-input-stream "<xml></xml>")
@@ -164,6 +171,15 @@
         (is (= {"id" 3, "foo" "bar"} (:params response)))
         (is (= {"foo" "bar"} (:json-params response)))))
 
+    (testing "key-fn"
+      (let [request  {:headers {"content-type" "application/json; charset=UTF-8"}
+                      :body (string-input-stream "{\"foo\": \"bar\"}")
+                      :params {"id" 3}}
+            handler  (wrap-json-params identity {:key-fn (fn [k] (.toUpperCase (name k)))})
+            response (handler request)]
+        (is (= {"id" 3, "FOO" "bar"} (:params response)))
+        (is (= {"FOO" "bar"} (:json-params response)))))
+
     (testing "json body with bigdecimals"
       (let [handler (wrap-json-params identity {:bigdecimals? true})
             request  {:headers {"content-type" "application/json; charset=UTF-8"}
@@ -313,6 +329,13 @@
       (is (= (get-in response [:headers "Content-Type"]) "application/json; charset=utf-8"))
       (is (= (:body response) "[\"foo\",\"bar\"]"))))
 
+  (testing "key-fn"
+    (let [handler  (constantly {:status 200 :headers {} :body {:foo "bar" :baz "quz"}})
+          response ((wrap-json-response handler {:key-fn (fn [k] (.toUpperCase (name k)))}) {})]
+      (is (= (get-in response [:headers "Content-Type"]) "application/json; charset=utf-8"))
+      (is (or (= "{\"FOO\":\"bar\",\"BAZ\":\"quz\"}" (:body response))
+              (= "{\"BAZ\":\"quz\",\"FOO\":\"bar\"}" (:body response))))))
+
   (testing "list body"
     (let [handler  (constantly {:status 200 :headers {} :body '(:foo :bar)})
           response ((wrap-json-response handler) {})]