diff --git a/spacy/lang.pxd b/spacy/lang.pxd
index ba9d0a779..e2c7c56e6 100644
--- a/spacy/lang.pxd
+++ b/spacy/lang.pxd
@@ -32,9 +32,6 @@ cdef class Lexicon:
     
     cdef PreshMap _dict
     
-    cdef list _string_features
-    cdef list _flag_features
-
 
 cdef class Language:
     cdef Pool _mem
diff --git a/spacy/lang.pyx b/spacy/lang.pyx
index 9323dc052..5042ff4b2 100644
--- a/spacy/lang.pyx
+++ b/spacy/lang.pyx
@@ -266,10 +266,10 @@ cdef class Lexicon:
     cpdef Lexeme lookup(self, unicode uni_string):
         """Retrieve (or create, if not found) a Lexeme for a string, and return it.
     
-        Args
+       Args
             string (unicode):  The string to be looked up. Must be unicode, not bytes.
 
-        Returns:
+       Returns:
             lexeme (Lexeme): A reference to a lexical type.
         """
         cdef String string
diff --git a/spacy/lexeme.pxd b/spacy/lexeme.pxd
index b39a32522..066f05b20 100644
--- a/spacy/lexeme.pxd
+++ b/spacy/lexeme.pxd
@@ -1,8 +1,7 @@
-from .typedefs cimport hash_t, utf8_t, flag_t, id_t
-
-from thinc.typedefs cimport atom_t
+from .typedefs cimport hash_t, utf8_t, flag_t, id_t, len_t, tag_t
 
 from .utf8string cimport StringStore
+from libc.stdint cimport uint16_t
 
 cpdef flag_t OOV_DIST_FLAGS
 
@@ -23,23 +22,24 @@ cpdef enum:
 
 
 cdef struct Lexeme:
-    atom_t length
+    flag_t flags
    
-    atom_t sic
-    atom_t norm
-    atom_t shape
-    atom_t vocab10k
-    atom_t asciied
-    atom_t prefix
-    atom_t suffix
-
-    atom_t cluster
-    atom_t pos
-    atom_t supersense
+    id_t sic
+    id_t norm
+    id_t shape
+    id_t vocab10k
+    id_t asciied
+    id_t prefix
+    id_t suffix
 
     float prob
+    
+    len_t length
+    tag_t cluster
+    tag_t pos
+    tag_t supersense
+
 
-    flag_t flags
 
 
 cdef Lexeme EMPTY_LEXEME
diff --git a/spacy/lexeme.pyx b/spacy/lexeme.pyx
index 6760b3913..62804621d 100644
--- a/spacy/lexeme.pyx
+++ b/spacy/lexeme.pyx
@@ -52,7 +52,7 @@ cpdef Lexeme init(unicode string, hash_t hashed,
     lex.flags = get_flags(string, upper_pc, title_pc, lower_pc)
     return lex
 
-cdef atom_t get_string_id(unicode string, StringStore store) except 0:
+cdef id_t get_string_id(unicode string, StringStore store) except 0:
     cdef bytes byte_string = string.encode('utf8')
     cdef Utf8Str* orig_str = store.intern(<char*>byte_string, len(byte_string))
     return orig_str.i
diff --git a/spacy/typedefs.pxd b/spacy/typedefs.pxd
index 34c327069..db6eb42ce 100644
--- a/spacy/typedefs.pxd
+++ b/spacy/typedefs.pxd
@@ -1,8 +1,10 @@
-from libc.stdint cimport uint64_t, uintptr_t
+from libc.stdint cimport uint16_t, uint32_t, uint64_t, uintptr_t
 
 ctypedef uint64_t hash_t
 ctypedef char* utf8_t
 ctypedef uint64_t flag_t
-ctypedef uintptr_t id_t
+ctypedef uint32_t id_t
+ctypedef uint16_t len_t
+ctypedef uint16_t tag_t