diff --git a/src/leap/soledad/client/_db/blobs/__init__.py b/src/leap/soledad/client/_db/blobs/__init__.py
index cacfe638b2dee8e35b72751428e883af1b01193c..517cfad41ea149abc5b6b1e04bf01cb698fb3fa4 100644
--- a/src/leap/soledad/client/_db/blobs/__init__.py
+++ b/src/leap/soledad/client/_db/blobs/__init__.py
@@ -105,9 +105,11 @@ class DecrypterBuffer(object):
             real_size = self.decrypter.decrypted_content_size
             return self.decrypter.endStream(), real_size
         elif hasattr(self, 'raw_data'):
-            # Externally encrypted blob, see Incoming API specification
+            # blob was not symmetrically encrypted, see _make_decryptor() above
             return self.raw_data, self.raw_data.tell()
         else:
+            # the only case that can lead here is if the preamble was not
+            # completelly consumed by the pipe.
             msg = "Incomplete Blob: %s" % self.doc_info.doc_id
             raise RetriableTransferError(msg)
 
diff --git a/tests/blobs/test_decrypter_buffer.py b/tests/blobs/test_decrypter_buffer.py
index db8ca5fa4ae6ace7cf6a96ccf3ace631f32a3c95..6b4a744ffbd5554845f294c416a54f3c6856224e 100644
--- a/tests/blobs/test_decrypter_buffer.py
+++ b/tests/blobs/test_decrypter_buffer.py
@@ -88,7 +88,7 @@ class DecrypterBufferCase(unittest.TestCase):
     @defer.inlineCallbacks
     def test_incomplete_blob_decryption(self):
         # SCENARIO: Transport failed and close was called with incomplete data
-        # CASE 1: Incomplete blob of known encryption type
+        # CASE 2: Incomplete blob of known encryption type
         # OUTCOME: InvalidBlob. It's safer to assume the tag is invalid
         encrypted = (yield self.blob.encrypt()).getvalue()
         encrypted = encrypted[:-20]  # 20 bytes missing