diff --git a/spacy/tokenizer.pyx b/spacy/tokenizer.pyx
index eea7e5ad1..0bf1aba6e 100644
--- a/spacy/tokenizer.pyx
+++ b/spacy/tokenizer.pyx
@@ -80,34 +80,37 @@ cdef class Tokenizer:
         cdef int i = 0
         cdef int start = 0
         cdef bint cache_hit
-        chars = <Py_UNICODE*>string
-        cdef bint in_ws = Py_UNICODE_ISSPACE(chars[0])
+        cdef bint in_ws = Py_UNICODE_ISSPACE(string[0])
         cdef unicode span
+        # Use of Py_UNICODE is deprecated, and I should be using Py_UCS4.
+        # But this is hard --- I need to acquire a pointer, but there's no
+        # Py_UCS4 API in Python 2.
+        cdef Py_UNICODE uc
+        cdef Py_UNICODE* chars_ptr = <Py_UNICODE*>string
         # The task here is much like string.split, but not quite
         # We find spans of whitespace and non-space characters, and ignore
         # spans that are exactly ' '. So, our sequences will all be separated
         # by either ' ' or nothing.
-        for i in range(1, length):
-            if Py_UNICODE_ISSPACE(chars[i]) != in_ws:
+        for i range(1, length):
+            uc = chars_ptr[i]
+            if Py_UNICODE_ISSPACE(uc) != in_ws:
                 if start < i:
-                    span = string[start:i]
-                    key = hash_string(span)
+                    key = hash64(chars_ptr, (i - start) * sizeof(Py_UNICODE), 0)
                     cache_hit = self._try_cache(key, tokens)
                     if not cache_hit:
-                        self._tokenize(tokens, span, key)
+                        self._tokenize(tokens, string[start:i], key)
                 in_ws = not in_ws
-                start = i
-                if chars[i] == ' ':
+                if uc == ' ':
                     tokens.data[tokens.length - 1].spacy = True
-                    start += 1
+                    start = i + 1
+                else:
+                    start = i
         i += 1
         if start < i:
-            span = string[start:i]
-            key = hash_string(span)
+            key = hash64(chars_ptr, (i - start) * sizeof(Py_UNICODE), 0)
             cache_hit = self._try_cache(key, tokens)
             if not cache_hit:
-                self._tokenize(tokens, span, key)
-
+                self._tokenize(tokens, string[start:], key)
             tokens.data[tokens.length - 1].spacy = string[-1] == ' '
         return tokens