diff --git a/nilmdb/client/client.py b/nilmdb/client/client.py
index c82e000..9fe3c6a 100644
--- a/nilmdb/client/client.py
+++ b/nilmdb/client/client.py
@@ -331,7 +331,7 @@ class StreamInserter(object):
         # Send the block once we have enough data
         if self._block_len >= maxdata:
             self._send_block(final = False)
-            if self._block_len >= self._max_data_after_send: # pragma: no cover
+            if self._block_len >= self._max_data_after_send:
                 raise ValueError("too much data left over after trying"
                                  " to send intermediate block; is it"
                                  " missing newlines or malformed?")
diff --git a/tests/test_client.py b/tests/test_client.py
index 38424ac..3f2a5e1 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -571,6 +571,12 @@ class TestClient(object):
             ctx.finalize()
             ctx.insert(b"# this is super long" * 100)
 
+            # override _max_data_after_send to trigger ValueError on a
+            # long nonterminated line
+            ctx._max_data_after_send = 1000
+            with assert_raises(ValueError):
+                ctx.insert(b"# this is super long" * 100)
+
         with assert_raises(ClientError):
             with client.stream_insert_context("/context/test",
                                               1000, 2000) as ctx: