diff --git a/src/cchardet/_cchardet.pyx b/src/cchardet/_cchardet.pyx
index 690d5f3..75af096 100644
--- a/src/cchardet/_cchardet.pyx
+++ b/src/cchardet/_cchardet.pyx
@@ -11,7 +11,7 @@ cdef extern from "uchardet.h":
     cdef const_char_ptr uchardet_get_charset(uchardet_t ud)
     cdef float uchardet_get_confidence(uchardet_t ud)
 
-def detect_with_confidence(const_char_ptr msg):
+def detect_with_confidence(bytes msg):
     cdef int length = len(msg)
     
     cdef uchardet_t ud = uchardet_new()
@@ -54,7 +54,7 @@ cdef class UniversalDetector:
             self._detected_confidence = 0.0
             uchardet_reset(self._ud)
 
-    def feed(self, const_char_ptr msg):
+    def feed(self, bytes msg):
         cdef int length
         cdef int result
 
diff --git a/src/tests/test.py b/src/tests/test.py
index 879fae5..2723ce0 100644
--- a/src/tests/test.py
+++ b/src/tests/test.py
@@ -114,3 +114,15 @@ class TestCChardet():
                 detected_encoding['encoding'].lower()
             )
         )
+
+    def test_null_bytes(self):
+        sample = b'ABC\x00\x80\x81'
+        detected_encoding = cchardet.detect(sample)
+
+        eq_(
+            None,
+            detected_encoding['encoding'],
+            'Expected None, but got %s' % (
+                detected_encoding['encoding']
+            )
+        )