diff --git a/scrapy/http/request/form.py b/scrapy/http/request/form.py
index d2ebf011a..50533ea42 100644
--- a/scrapy/http/request/form.py
+++ b/scrapy/http/request/form.py
@@ -77,11 +77,11 @@ def _get_inputs(form, formdata, dont_click, clickdata, response):
     except (ValueError, TypeError):
         raise ValueError('formdata should be a dict or iterable of tuples')
 
-    inputs = [(n, v) for n, v in form.form_values() if n not in formdata]
+    inputs = [(n, u'' if v is None else v) for n, v in form.fields.items() if n not in formdata]
 
     if not dont_click:
         clickable = _get_clickable(clickdata, form)
-        if clickable and clickable[0] not in formdata:
+        if clickable and clickable[0] not in formdata and not clickable[0] is None:
             inputs.append(clickable)
 
     inputs.extend(formdata.iteritems())
diff --git a/scrapy/tests/test_http_request.py b/scrapy/tests/test_http_request.py
index 8a590f7eb..2110e73f4 100644
--- a/scrapy/tests/test_http_request.py
+++ b/scrapy/tests/test_http_request.py
@@ -496,6 +496,33 @@ class FormRequestTest(RequestTest):
         response = HtmlResponse("http://www.example.com/formname.html", body=respbody)
         self.assertRaises(IndexError, self.request_class.from_response, response, formname="form3", formnumber=2)
 
+    def test_from_response_missed_value(self):
+        respbody = """
+<form action="get.php" method="POST">
+    <input type="hidden" name="key1" value="val1">
+    <input type="hidden" name="key2">
+    <input type="radio" name="key3" checked>
+    <input type="checkbox" name="key4" checked>
+    <textarea name="key5">val5</textarea>
+    <textarea name="key6"/>
+    <select name="key7">
+        <option name="opt1" selected></option>
+        <option name="opt2">opt2</option>
+    </select>
+    <input type="submit" value="val8">
+</form>
+        """
+        res = HtmlResponse("http://example.com", body=respbody, encoding='utf-8')
+        req = self.request_class.from_response(res)
+        fs = cgi.parse_qs(req.body, True)
+        self.assertEqual(fs['key1'], ['val1'])
+        self.assertEqual(fs['key2'], [''])
+        self.assertEqual(fs['key3'], ['on'])
+        self.assertEqual(fs['key4'], ['on'])
+        self.assertEqual(fs['key5'], ['val5'])
+        self.assertEqual(fs['key6'], [''])
+        self.assertEqual(fs['key7'], [''])
+        self.assertEqual(set(fs), set(['key1', 'key2', 'key3', 'key4', 'key5', 'key6', 'key7']))
 
 class XmlRpcRequestTest(RequestTest):