diff --git a/nibabel/streamlines/array_sequence.py b/nibabel/streamlines/array_sequence.py
index d892b9b91d..91e94d7ac1 100644
--- a/nibabel/streamlines/array_sequence.py
+++ b/nibabel/streamlines/array_sequence.py
@@ -37,7 +37,7 @@ def __init__(self, arr_seq, common_shape, dtype):
         self.common_shape = common_shape
         n_in_row = reduce(mul, common_shape, 1)
         bytes_per_row = n_in_row * dtype.itemsize
-        self.rows_per_buf = bytes_per_row / self.bytes_per_buf
+        self.rows_per_buf = max(1, self.bytes_per_buf // bytes_per_row)
 
     def update_seq(self, arr_seq):
         arr_seq._offsets = np.array(self.offsets)
@@ -185,6 +185,7 @@ def finalize_append(self):
             return
         self._build_cache.update_seq(self)
         self._build_cache = None
+        self.shrink_data()
 
     def _resize_data_to(self, n_rows, build_cache):
         """ Resize data array if required """
diff --git a/nibabel/streamlines/tests/test_array_sequence.py b/nibabel/streamlines/tests/test_array_sequence.py
index 6925f58b35..45f50075f8 100644
--- a/nibabel/streamlines/tests/test_array_sequence.py
+++ b/nibabel/streamlines/tests/test_array_sequence.py
@@ -2,6 +2,7 @@
 import sys
 import unittest
 import tempfile
+import itertools
 import numpy as np
 
 from nose.tools import assert_equal, assert_raises, assert_true
@@ -91,11 +92,20 @@ def test_creating_arraysequence_from_list(self):
                       SEQ_DATA['data'])
 
     def test_creating_arraysequence_from_generator(self):
-        gen = (e for e in SEQ_DATA['data'])
-        check_arr_seq(ArraySequence(gen), SEQ_DATA['data'])
+        gen_1, gen_2 = itertools.tee((e for e in SEQ_DATA['data']))
+        seq = ArraySequence(gen_1)
+        seq_with_buffer = ArraySequence(gen_2, buffer_size=256)
+
+        # Check buffer size effect
+        assert_equal(seq_with_buffer.data.shape, seq.data.shape)
+        assert_true(seq_with_buffer._buffer_size > seq._buffer_size)
+
+        # Check generator result
+        check_arr_seq(seq, SEQ_DATA['data'])
+        check_arr_seq(seq_with_buffer, SEQ_DATA['data'])
 
         # Already consumed generator
-        check_empty_arr_seq(ArraySequence(gen))
+        check_empty_arr_seq(ArraySequence(gen_1))
 
     def test_creating_arraysequence_from_arraysequence(self):
         seq = ArraySequence(SEQ_DATA['data'])