diff --git a/_crc32c.c b/_crc32c.c
index 1d0f58f..4462d06 100644
--- a/_crc32c.c
+++ b/_crc32c.c
@@ -37,10 +37,13 @@ static crc_function crc_fn;
 int is_big_endian;
 
 static
-PyObject* crc32c_crc32c(PyObject *self, PyObject *args) {
+PyObject* crc32c_crc32c(PyObject *self, PyObject *args, PyObject *kwargs) {
 	Py_buffer pbin;
 	unsigned char *bin_data = NULL;
 	uint32_t crc = 0U, result;
+	int release_gil = -1;
+
+	static char *kwlist[] = {"inp", "crc", "release_gil", NULL};
 
 	/* In python 3 we accept only bytes-like objects */
 	const char *format =
@@ -49,31 +52,37 @@ PyObject* crc32c_crc32c(PyObject *self, PyObject *args) {
 #else
 	"s*"
 #endif
-	"|I:crc32";
+	"|Ii:crc32";
 
-	if (!PyArg_ParseTuple(args, format, &pbin, &crc) )
+	if (!PyArg_ParseTupleAndKeywords(args, kwargs, format, kwlist, &pbin, &crc, &release_gil) )
 		return NULL;
 
 	bin_data = pbin.buf;
-	Py_BEGIN_ALLOW_THREADS
-	crc ^= 0xffffffff;
-	result = crc_fn(crc, bin_data, pbin.len);
-	result ^= 0xffffffff;
-	Py_END_ALLOW_THREADS
+	if ((release_gil < 0 && pbin.len >= 32768) || release_gil >= 1) {
+		Py_BEGIN_ALLOW_THREADS
+		crc ^= 0xffffffff;
+		result = crc_fn(crc, bin_data, pbin.len);
+		result ^= 0xffffffff;
+		Py_END_ALLOW_THREADS
+	} else {
+		crc ^= 0xffffffff;
+		result = crc_fn(crc, bin_data, pbin.len);
+		result ^= 0xffffffff;
+	}
 
 	PyBuffer_Release(&pbin);
 	return PyLong_FromUnsignedLong(result);
 }
 
 static
-PyObject *crc32c_crc32(PyObject *self, PyObject *args)
+PyObject *crc32c_crc32(PyObject *self, PyObject *args, PyObject *kwargs)
 {
 	if (PyErr_WarnEx(PyExc_DeprecationWarning,
-	                 "crc32c.crc32 will be eventually removed, use crc32c.crc32c instead",
-	                 1) == -1) {
+					 "crc32c.crc32 will be eventually removed, use crc32c.crc32c instead",
+					 1) == -1) {
 		return NULL;
 	}
-	return crc32c_crc32c(self, args);
+	return crc32c_crc32c(self, args, kwargs);
 }
 
 /* The different values the SW mode preference can take */
@@ -103,8 +112,8 @@ static enum crc32c_sw_mode get_sw_mode(void)
 }
 
 static PyMethodDef CRC32CMethods[] = {
-	{"crc32",   crc32c_crc32,   METH_VARARGS, "Calculate crc32c incrementally (deprecated)"},
-	{"crc32c",  crc32c_crc32c,  METH_VARARGS, "Calculate crc32c incrementally"},
+	{"crc32",   (PyCFunction)crc32c_crc32,   METH_VARARGS | METH_KEYWORDS, "Calculate crc32c incrementally (deprecated)"},
+	{"crc32c",  (PyCFunction)crc32c_crc32c,  METH_VARARGS | METH_KEYWORDS, "Calculate crc32c incrementally"},
 	{NULL, NULL, 0, NULL}        /* Sentinel */
 };
 
diff --git a/test/test_crc32c.py b/test/test_crc32c.py
index 480610a..2deea66 100644
--- a/test/test_crc32c.py
+++ b/test/test_crc32c.py
@@ -80,6 +80,9 @@ class TestMisc(unittest.TestCase):
     def test_zero(self):
         self.assertEqual(0, crc32c.crc32c(b''))
 
+    def test_keyword(self):
+        self.assertEqual(10, crc32c.crc32c(b'', crc=10))
+
     def test_crc32_deprecated(self):
         with warning_catcher() as warns:
             crc32c.crc32(b'')