diff --git a/requests/models.py b/requests/models.py
index b4cdead4..fe554ffc 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -780,7 +780,6 @@ class Response(object):
 
         for chunk in self.iter_content(chunk_size=chunk_size,
                                        decode_unicode=decode_unicode):
-
             # Skip any null responses
             if not chunk:
                 continue
@@ -796,15 +795,23 @@ class Response(object):
             else:
                 lines = chunk.splitlines()
 
-            # The split(delimiter) will always end with whatever remains past
-            # the delimiter ('' if nothing more).  However splitlines() will
-            # not end with a '' if the final text is a line delimiter.
-
-            # Therefore, if we're in delimiter mode, always pop the final
-            # item to prepend to the next chunk. However, only do this for
-            # non-delimiter mode if the chunk does not match the end of the
-            # last line.
-            if delimiter or (lines[-1] and lines[-1][-1] == chunk[-1]):
+            # Calling `.split(delimiter)` will always end with whatever text
+            # remains beyond the delimiter, or '' if the delimiter is the end
+            # of the text.  On the other hand, `.splitlines()` doesn't include
+            # a '' if the text ends in a line delimiter.
+            #
+            # For example:
+            #
+            #     'abc\ndef\n'.split('\n')  ~> ['abc', 'def', '']
+            #     'abc\ndef\n'.splitlines() ~> ['abc', 'def']
+            #
+            # So if we have a specified delimiter, we always pop the final
+            # item and prepend it to the next chunk.
+            #
+            # If we're using `splitlines()`, we only do this if the chunk
+            # ended midway through a line.
+            incomplete_line = (lines[-1] and lines[-1].endswith(chunk[-1]))
+            if delimiter or incomplete_line:
                 pending = lines.pop()
 
             for line in lines:
diff --git a/tests/test_requests.py b/tests/test_requests.py
index d56e365a..76a2d45a 100755
--- a/tests/test_requests.py
+++ b/tests/test_requests.py
@@ -1296,10 +1296,11 @@ class TestRequests:
         assert r.request.url == pr.request.url
         assert r.request.headers == pr.request.headers
 
+
     def test_response_lines(self):
         """
-        iter_lines should be able to handle data dribbling in which might
-        not be lined up ideally.
+        iter_lines should be able to handle data dribbling in which delimiters
+        might not be lined up ideally.
         """
         mock_chunks = [
             'This \r\n',
@@ -1315,6 +1316,7 @@ class TestRequests:
             '\n',
             'end.',
         ]
+        mock_data = ''.join(mock_chunks)
 
         def mock_iter_content(*args, **kwargs):
             '''Fake difficult data.'''
@@ -1325,16 +1327,17 @@ class TestRequests:
         r._content_consumed = True
         r.iter_content = mock_iter_content
 
-        assert list(r.iter_lines(delimiter='\r\n')) == \
-            ''.join(mock_chunks).split('\r\n')
+        assert list(r.iter_lines(delimiter='\r\n')) == mock_data.split('\r\n')
 
-        # This test can't pass because '\n' by itself is a single line-end, but
-        # '\r\n' is also a single line-end
-        assert not (list(r.iter_lines()) == ''.join(mock_chunks).splitlines())
+        # Because '\n' is a single line-end, when `iter_lines()` receives
+        # the chunks containing a single '\n', it emits '' as a line -- whereas
+        # `.splitlines()` combines with the '\r' and splits on `\r\n`.
+        assert list(r.iter_lines()) != mock_data.splitlines()
 
-        # However, this should pass if everything is '\r'
+        # If we change all the line breaks to `\r`, we should be okay.
         mock_chunks = [chunk.replace('\n', '\r') for chunk in mock_chunks]
-        assert list(r.iter_lines()) == ''.join(mock_chunks).splitlines()
+        mock_data = ''.join(mock_chunks)
+        assert list(r.iter_lines()) == mock_data.splitlines()
 
     def test_prepared_request_is_pickleable(self, httpbin):
         p = requests.Request('GET', httpbin('get')).prepare()