diff --git a/aiohttp/multipart.py b/aiohttp/multipart.py
index 35f0f8f1164..47caad26d49 100644
--- a/aiohttp/multipart.py
+++ b/aiohttp/multipart.py
@@ -214,6 +214,7 @@ def __init__(self, boundary, headers, content):
         self._read_bytes = 0
         self._unread = deque()
         self._prev_chunk = None
+        self._content_eof = 0
 
     @asyncio.coroutine
     def __aiter__(self):
@@ -310,13 +311,14 @@ def _read_chunk_from_stream(self, size):
             self._prev_chunk = yield from self._content.read(size)
 
         chunk = yield from self._content.read(size)
-
+        self._content_eof += int(self._content.at_eof())
+        assert self._content_eof < 3, "Reading after EOF"
         window = self._prev_chunk + chunk
         sub = b'\r\n' + self._boundary
         if first_chunk:
             idx = window.find(sub)
         else:
-            idx = window.find(sub, len(self._prev_chunk) - len(sub))
+            idx = window.find(sub, max(0, len(self._prev_chunk) - len(sub)))
         if idx >= 0:
             # pushing boundary back to content
             self._content.unread_data(window[idx:])
@@ -325,6 +327,10 @@ def _read_chunk_from_stream(self, size):
             chunk = window[len(self._prev_chunk):idx]
             if not chunk:
                 self._at_eof = True
+        if 0 < len(chunk) < len(sub) and not self._content_eof:
+            self._prev_chunk += chunk
+            self._at_eof = False
+            return b''
         result = self._prev_chunk
         self._prev_chunk = chunk
         return result
diff --git a/tests/test_multipart.py b/tests/test_multipart.py
index bd736a261e2..cb39656ad4d 100644
--- a/tests/test_multipart.py
+++ b/tests/test_multipart.py
@@ -69,6 +69,9 @@ def __init__(self, content):
     def read(self, size=None):
         return self.content.read(size)
 
+    def at_eof(self):
+        return self.content.tell() == len(self.content.getbuffer())
+
     @asyncio.coroutine
     def readline(self):
         return self.content.readline()
@@ -191,6 +194,47 @@ def prepare(data):
             c3 = yield from obj.read_chunk(8)
             self.assertEqual(c3, b'!')
 
+    def test_read_all_at_once(self):
+        stream = Stream(b'Hello, World!\r\n--:--\r\n')
+        obj = aiohttp.multipart.BodyPartReader(self.boundary, {}, stream)
+        result = yield from obj.read_chunk()
+        self.assertEqual(b'Hello, World!', result)
+        result = yield from obj.read_chunk()
+        self.assertEqual(b'', result)
+        self.assertTrue(obj.at_eof())
+
+    def test_read_incomplete_body_chunked(self):
+        stream = Stream(b'Hello, World!\r\n-')
+        obj = aiohttp.multipart.BodyPartReader(self.boundary, {}, stream)
+        result = b''
+        with self.assertRaises(AssertionError):
+            for _ in range(4):
+                result += yield from obj.read_chunk(7)
+        self.assertEqual(b'Hello, World!\r\n-', result)
+
+    def test_read_boundary_with_incomplete_chunk(self):
+        stream = Stream(b'')
+
+        def prepare(data):
+            f = asyncio.Future(loop=self.loop)
+            f.set_result(data)
+            return f
+
+        with mock.patch.object(stream, 'read', side_effect=[
+            prepare(b'Hello, World'),
+            prepare(b'!\r\n'),
+            prepare(b'--:'),
+            prepare(b'')
+        ]):
+            obj = aiohttp.multipart.BodyPartReader(
+                self.boundary, {}, stream)
+            c1 = yield from obj.read_chunk(12)
+            self.assertEqual(c1, b'Hello, World')
+            c2 = yield from obj.read_chunk(8)
+            self.assertEqual(c2, b'!')
+            c3 = yield from obj.read_chunk(8)
+            self.assertEqual(c3, b'')
+
     def test_multi_read_chunk(self):
         stream = Stream(b'Hello,\r\n--:\r\n\r\nworld!\r\n--:--')
         obj = aiohttp.multipart.BodyPartReader(self.boundary, {}, stream)