diff --git a/docs/release.rst b/docs/release.rst
index b569015c..17f146e9 100644
--- a/docs/release.rst
+++ b/docs/release.rst
@@ -26,7 +26,8 @@ Enhancements
 
 Fix
 ~~~
-
+* Fix VLenUTF8 encoding for read-only buffers.
+  By :user:`Isaac Virshup <ivirshup>`, :issue:`514`.
 * Fix skip of entry points backport tests
   By :user:`Elliott Sales de Andrade <QuLogic>`, :issue:`487`.
 * Fix Upgrade to Zstd 1.5.5 due to potential corruption.
diff --git a/numcodecs/tests/test_vlen_utf8.py b/numcodecs/tests/test_vlen_utf8.py
index c2ee525b..4501d929 100644
--- a/numcodecs/tests/test_vlen_utf8.py
+++ b/numcodecs/tests/test_vlen_utf8.py
@@ -82,8 +82,11 @@ def test_decode_errors():
         codec.decode(enc, out=np.zeros(10, dtype='i4'))
 
 
-def test_encode_utf8():
+@pytest.mark.parametrize("writable", [True, False])
+def test_encode_utf8(writable):
     a = np.array(['foo', None, 'bar'], dtype=object)
+    if not writable:
+        a.setflags(write=False)
     codec = VLenUTF8()
     enc = codec.encode(a)
     dec = codec.decode(enc)
diff --git a/numcodecs/vlen.pyx b/numcodecs/vlen.pyx
index a1ff0e26..e1e149ee 100644
--- a/numcodecs/vlen.pyx
+++ b/numcodecs/vlen.pyx
@@ -7,6 +7,7 @@
 
 import cython
 cimport cython
+from numpy cimport ndarray
 import numpy as np
 from .abc import Codec
 from .compat_ext cimport Buffer
@@ -74,7 +75,7 @@ class VLenUTF8(Codec):
     def encode(self, buf):
         cdef:
             Py_ssize_t i, l, n_items, data_length, total_length
-            object[:] input_values
+            ndarray[object, ndim=1] input_values
             object[:] encoded_values
             int[:] encoded_lengths
             char* encv
diff --git a/pyproject.toml b/pyproject.toml
index 319b29d7..af8f040a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,7 +3,8 @@ requires = [
     "setuptools>=64",
     "setuptools-scm[toml]>=6.2",
     "Cython",
-    "py-cpuinfo"
+    "py-cpuinfo",
+    "numpy",
 ]
 build-backend = "setuptools.build_meta"
 
diff --git a/setup.py b/setup.py
index ea8bc64c..e594a203 100644
--- a/setup.py
+++ b/setup.py
@@ -196,12 +196,13 @@ def lz4_extension():
 
 def vlen_extension():
     info('setting up vlen extension')
+    import numpy
 
     extra_compile_args = base_compile_args.copy()
     define_macros = []
 
     # setup sources
-    include_dirs = ['numcodecs']
+    include_dirs = ['numcodecs', numpy.get_include()]
     # define_macros += [('CYTHON_TRACE', '1')]
 
     sources = ['numcodecs/vlen.pyx']