diff --git a/scrapy/http/request/json_request.py b/scrapy/http/request/json_request.py
index 0fdd2ddf1..03a0ab061 100644
--- a/scrapy/http/request/json_request.py
+++ b/scrapy/http/request/json_request.py
@@ -12,17 +12,13 @@ from scrapy.http.request import Request
 
 class JSONRequest(Request):
     def __init__(self, *args, **kwargs):
-        if 'method' not in kwargs:
-            kwargs['method'] = 'POST'
+        data = kwargs.pop('data', None)
+        if data:
+            kwargs['body'] = json.dumps(data)
+
+            if 'method' not in kwargs:
+                kwargs['method'] = 'POST'
 
-        data = kwargs.pop('data', {})
-        kwargs['body'] = json.dumps(data)
         super(JSONRequest, self).__init__(*args, **kwargs)
-        self.headers.setdefault(b'Content-Type', b'application/json')
-
-    def replace(self, *args, **kwargs):
-        """ Create a new Request with the same attributes except for those
-            given new values. """
-
-        kwargs.pop('body', None)
-        return super(JSONRequest, self).replace(*args, **kwargs)
+        self.headers.setdefault('Content-Type', 'application/json')
+        self.headers.setdefault('Accept', 'application/json, text/javascript, */*; q=0.01')
diff --git a/tests/test_http_request.py b/tests/test_http_request.py
index a2021bd65..793a583bc 100644
--- a/tests/test_http_request.py
+++ b/tests/test_http_request.py
@@ -1150,54 +1150,29 @@ class XmlRpcRequestTest(RequestTest):
 
 class JSONRequestTest(RequestTest):
     request_class = JSONRequest
-    default_method = 'POST'
-    default_headers = {b'Content-Type': [b'application/json']}
+    default_method = 'GET'
+    default_headers = {b'Content-Type': [b'application/json'], b'Accept': [b'application/json, text/javascript, */*; q=0.01']}
 
-    def test_body(self):
+    def test_data(self):
         r1 = self.request_class(url="http://www.example.com/")
-        self.assertEqual(r1.body, b'{}')
+        self.assertEqual(r1.body, b'')
+        self.assertEqual(r1.method, 'GET')
 
-        r2 = self.request_class(url="http://www.example.com/", body=b"")
-        self.assertEqual(r2.body, b'{}')
+        body = b'body'
+        r2 = self.request_class(url="http://www.example.com/", body=body)
+        self.assertEqual(r2.body, body)
+        self.assertEqual(r2.method, 'GET')
 
         data = {
             'name': 'value',
         }
         r3 = self.request_class(url="http://www.example.com/", data=data)
         self.assertEqual(r3.body, to_bytes(json.dumps(data)))
+        self.assertEqual(r3.method, 'POST')
 
-        r4 = self.request_class(url="http://www.example.com/", body='body1', data=data)
-        self.assertEqual(r3.body, to_bytes(json.dumps(data)))
-
-    def test_replace(self):
-        """Test Request.replace() method"""
-        r1 = self.request_class("http://www.example.com")
-        hdrs = Headers(r1.headers)
-        hdrs[b'key'] = b'value'
-        r2 = r1.replace(body="New body", headers=hdrs)
-
-        # body will not be replaced
-        self.assertEqual(r1.body, r2.body)
-        self.assertEqual(r1.url, r2.url)
-        self.assertEqual((r1.headers, r2.headers), (self.default_headers, hdrs))
-
-        # Empty attributes (which may fail if not compared properly)
-        r3 = self.request_class("http://www.example.com", meta={'a': 1}, dont_filter=True)
-        r4 = r3.replace(url="http://www.example.com/2", meta={}, dont_filter=False)
-        self.assertEqual(r4.url, "http://www.example.com/2")
-        self.assertEqual(r4.meta, {})
-        assert r4.dont_filter is False
-
-        data1 = {
-            'name': 'value1',
-        }
-        data2 = {
-            'name': 'value2',
-        }
-        r5 = self.request_class("http://www.example.com", data=data1)
-        r6 = r5.replace(url="http://www.example.com/2", data=data2)
-        self.assertNotEqual(r5.body, r6.body)
-        self.assertEqual((r5.body, r6.body), (to_bytes(json.dumps(data1)), to_bytes(json.dumps(data2))))
+        r4 = self.request_class(url="http://www.example.com/", body=body, data=data)
+        self.assertEqual(r4.body, to_bytes(json.dumps(data)))
+        self.assertEqual(r4.method, 'POST')
 
 
 if __name__ == "__main__":