diff --git a/spacy/lexeme.pyx b/spacy/lexeme.pyx
index 66867a648..26acff407 100644
--- a/spacy/lexeme.pyx
+++ b/spacy/lexeme.pyx
@@ -43,6 +43,8 @@ cdef class Lexeme:
         return True if Lexeme.c_check_flag(self.c, flag_id) else False
 
     def similarity(self, other):
+        if self.vector_norm == 0 or other.vector_norm == 0:
+            return 0.0
         return numpy.dot(self.vector, other.vector) / (self.vector_norm * other.vector_norm)
 
     property has_vector:
diff --git a/spacy/tokens/doc.pyx b/spacy/tokens/doc.pyx
index 19cff3a90..536b3582b 100644
--- a/spacy/tokens/doc.pyx
+++ b/spacy/tokens/doc.pyx
@@ -127,6 +127,8 @@ cdef class Doc:
         return u''.join([t.string for t in self])
 
     def similarity(self, other):
+        if self.vector_norm == 0 or other.vector_norm == 0:
+            return 0.0
         return numpy.dot(self.vector, other.vector) / (self.vector_norm * other.vector_norm)
 
     property repvec:
diff --git a/spacy/tokens/spans.pyx b/spacy/tokens/spans.pyx
index 38b9ebcca..cca24cb5b 100644
--- a/spacy/tokens/spans.pyx
+++ b/spacy/tokens/spans.pyx
@@ -60,6 +60,8 @@ cdef class Span:
         self._seq.merge(self[0].idx, self[-1].idx + len(self[-1]), tag, lemma, ent_type)
 
     def similarity(self, other):
+        if self.vector_norm == 0.0 or other.vector_norm == 0.0:
+            return 0.0
         return numpy.dot(self.vector, other.vector) / (self.vector_norm * other.vector_norm)
 
     property vector:
diff --git a/spacy/tokens/token.pyx b/spacy/tokens/token.pyx
index 4f8effa4e..25db3f47e 100644
--- a/spacy/tokens/token.pyx
+++ b/spacy/tokens/token.pyx
@@ -50,6 +50,8 @@ cdef class Token:
         return self.doc[self.i+i]
 
     def similarity(self, other):
+        if self.vector_norm == 0 or other.vector_norm == 0:
+            return 0.0
         return numpy.dot(self.vector, other.vector) / (self.vector_norm * other.vector_norm)
 
     property lex_id:
diff --git a/spacy/vocab.pyx b/spacy/vocab.pyx
index bb256b02e..e3ac67bf7 100644
--- a/spacy/vocab.pyx
+++ b/spacy/vocab.pyx
@@ -1,6 +1,5 @@
 from __future__ import unicode_literals
 
-
 from libc.stdio cimport fopen, fclose, fread, fwrite, FILE
 from libc.string cimport memset
 from libc.stdint cimport int32_t
@@ -117,16 +116,14 @@ cdef class Vocab:
 
     cdef const LexemeC* _new_lexeme(self, Pool mem, unicode string) except NULL:
         cdef hash_t key
-        #cdef bint is_oov = mem is not self.mem
-        # TODO
-        is_oov = False
-        mem = self.mem
+        cdef bint is_oov = mem is not self.mem
         if len(string) < 3:
             mem = self.mem
         lex = <LexemeC*>mem.alloc(sizeof(LexemeC), 1)
         lex.orth = self.strings[string]
         lex.length = len(string)
         lex.id = self.length
+        lex.repvec = <float*>mem.alloc(self.vectors_length, sizeof(float))
         if self.get_lex_attr is not None:
             for attr, func in self.get_lex_attr.items():
                 value = func(string)
@@ -283,7 +280,7 @@ cdef class Vocab:
                                                            vec_len, len(pieces))
                 orth = self.strings[word_str]
                 lexeme = <LexemeC*><void*>self.get_by_orth(self.mem, orth)
-                lexeme.repvec = <float*>self.mem.alloc(len(pieces), sizeof(float))
+                lexeme.repvec = <float*>self.mem.alloc(self.vectors_length, sizeof(float))
 
                 for i, val_str in enumerate(pieces):
                     lexeme.repvec[i] = float(val_str)