diff --git a/mechanicalsoup/browser.py b/mechanicalsoup/browser.py
index 35e40473..3979c647 100644
--- a/mechanicalsoup/browser.py
+++ b/mechanicalsoup/browser.py
@@ -155,6 +155,8 @@ def _request(self, form, url=None, **kwargs):
         # Requests also retains order when encoding form data in 2-tuple lists.
         data = [(k, v) for k, v in data.items()]
 
+        multipart = form.get("enctype", "") == "multipart/form-data"
+
         # Process form tags in the order that they appear on the page,
         # skipping those tags that do not have a name-attribute.
         selector = ",".join("{}[name]".format(i) for i in
@@ -175,18 +177,17 @@ def _request(self, form, url=None, **kwargs):
                     # browsers use empty string for inputs with missing values
                     value = tag.get("value", "")
 
-                if tag.get("type", "").lower() == "file":
-                    # read http://www.cs.tut.fi/~jkorpela/forms/file.html
-                    # in browsers, file upload only happens if the form
-                    # (or submit button) enctype attribute is set to
-                    # "multipart/form-data". We don't care, simplify.
+                # If the enctype is not multipart, the filename is put in
+                # the form as a text input and the file is not sent.
+                if tag.get("type", "").lower() == "file" and multipart:
                     filename = value
                     if filename != "" and isinstance(filename, string_types):
                         content = open(filename, "rb")
                     else:
                         content = ""
-                    # If value is the empty string, we still pass it for
-                    # consistency with browsers (see #250).
+                    # If value is the empty string, we still pass it
+                    # for consistency with browsers (see
+                    # https://github.com/MechanicalSoup/MechanicalSoup/issues/250).
                     files[name] = (filename, content)
                 else:
                     data.append((name, value))
@@ -223,6 +224,22 @@ def _request(self, form, url=None, **kwargs):
         else:
             kwargs["data"] = data
 
+        # The following part of the function is here to respect the
+        # enctype specified by the form, i.e. force sending multipart
+        # content. Since Requests doesn't have yet a feature to choose
+        # enctype, we have to use tricks to make it behave as we want
+        # This code will be updated if Requests implements it.
+        if multipart and not files:
+            # Requests will switch to "multipart/form-data" only if
+            # files pass the `if files:` test, so in this case we use
+            # a modified dict that passes the if test even if empty.
+            class DictThatReturnsTrue(dict):
+                def __bool__(self):
+                    return True
+                __nonzero__ = __bool__
+
+            files = DictThatReturnsTrue()
+
         return self.session.request(method, url, files=files, **kwargs)
 
     def submit(self, form, url=None, **kwargs):
diff --git a/tests/test_browser.py b/tests/test_browser.py
index 3280afa3..e16ec7f3 100644
--- a/tests/test_browser.py
+++ b/tests/test_browser.py
@@ -111,9 +111,8 @@ def test_enctype_and_file_submit(httpbin, enctype, submit_file, file_field):
     """.format(httpbin.url, enctype, file_field)
     form = BeautifulSoup(form_html, "lxml").form
 
-    # For now, assume that the encoding always allow sending file's
-    # content.
-    valid_enctype = True
+    valid_enctype = (enctype in valid_enctypes_file_submit and
+                     valid_enctypes_file_submit[enctype])
     expected_content = b""  # default
     if submit_file and file_field:
         # create a temporary file for testing file upload
@@ -133,10 +132,10 @@ def test_enctype_and_file_submit(httpbin, enctype, submit_file, file_field):
     browser = mechanicalsoup.Browser()
     response = browser._request(form)
 
-    if file_field:
-        expected_enctype = 'multipart/form-data'
+    if enctype not in valid_enctypes_file_submit:
+        expected_enctype = default_enctype
     else:
-        expected_enctype = 'application/x-www-form-urlencoded'
+        expected_enctype = enctype
     assert expected_enctype in response.request.headers["Content-Type"]
 
     resp = response.json()
@@ -153,6 +152,8 @@ def test_enctype_and_file_submit(httpbin, enctype, submit_file, file_field):
                 assert key in ("files", "form")
                 found = True
                 found_in = key
+            if key == "files" and not valid_enctype:
+                assert not value
 
     assert found == bool(file_field)
     if file_field: