diff --git a/docs/release.rst b/docs/release.rst
index 13c2f20d2c..7a5cf51db7 100644
--- a/docs/release.rst
+++ b/docs/release.rst
@@ -14,6 +14,9 @@ Bug fixes
   value when empty chunks are read back in.
   By :user:`Vyas Ramasubramani <vyasr>`; :issue:`965`.
 
+* Add number encoder for ``json.dumps`` to support numpy intergers in
+  ``chunks`` arguments. By :user:`Eric Prestat <ericpre>` :issue:`697`.
+
 .. _release_2.11.1:
 
 2.11.1
diff --git a/zarr/tests/test_creation.py b/zarr/tests/test_creation.py
index cfab4f79ec..ee99bc7c9f 100644
--- a/zarr/tests/test_creation.py
+++ b/zarr/tests/test_creation.py
@@ -714,3 +714,8 @@ def test_create_read_only(zarr_version):
     assert z.read_only
     with pytest.raises(PermissionError):
         z[:] = 42
+
+
+def test_json_dumps_chunks_numpy_dtype():
+    z = zeros((10,), chunks=(np.int64(2),))
+    assert np.all(z[...] == 0)
diff --git a/zarr/tests/test_util.py b/zarr/tests/test_util.py
index efe8e66341..e9e1786abe 100644
--- a/zarr/tests/test_util.py
+++ b/zarr/tests/test_util.py
@@ -4,8 +4,10 @@
 import numpy as np
 import pytest
 
-from zarr.util import (all_equal, flatten, guess_chunks, human_readable_size, info_html_report,
-                       info_text_report, is_total_slice, normalize_chunks,
+from zarr.core import Array
+from zarr.util import (all_equal, flatten, guess_chunks, human_readable_size,
+                       info_html_report, info_text_report, is_total_slice,
+                       json_dumps, normalize_chunks,
                        normalize_dimension_separator,
                        normalize_fill_value, normalize_order,
                        normalize_resize_args, normalize_shape, retry_call,
@@ -238,3 +240,11 @@ def test_all_equal():
     # all_equal(None, *) always returns False
     assert not all_equal(None, np.array([None, None]))
     assert not all_equal(None, np.array([None, 10]))
+
+
+def test_json_dumps_numpy_dtype():
+    assert json_dumps(np.int64(0)) == json_dumps(0)
+    assert json_dumps(np.float32(0)) == json_dumps(float(0))
+    # Check that we raise the error of the superclass for unsupported object
+    with pytest.raises(TypeError):
+        json_dumps(Array)
diff --git a/zarr/util.py b/zarr/util.py
index 9f5f04f525..cc3bd50356 100644
--- a/zarr/util.py
+++ b/zarr/util.py
@@ -33,10 +33,22 @@ def flatten(arg: Iterable) -> Iterable:
 }
 
 
+class NumberEncoder(json.JSONEncoder):
+
+    def default(self, o):
+        # See json.JSONEncoder.default docstring for explanation
+        # This is necessary to encode numpy dtype
+        if isinstance(o, numbers.Integral):
+            return int(o)
+        if isinstance(o, numbers.Real):
+            return float(o)
+        return json.JSONEncoder.default(self, o)
+
+
 def json_dumps(o: Any) -> bytes:
     """Write JSON in a consistent, human-readable way."""
     return json.dumps(o, indent=4, sort_keys=True, ensure_ascii=True,
-                      separators=(',', ': ')).encode('ascii')
+                      separators=(',', ': '), cls=NumberEncoder).encode('ascii')
 
 
 def json_loads(s: str) -> Dict[str, Any]: