diff --git a/spacy/vocab.pyx b/spacy/vocab.pyx
index d0df37317..bb256b02e 100644
--- a/spacy/vocab.pyx
+++ b/spacy/vocab.pyx
@@ -263,9 +263,10 @@ cdef class Vocab:
 
     def load_vectors(self, loc):
         if loc.endswith('bz2'):
-            self.load_vectors_bz2(loc)
+            vec_len = self.load_vectors_bz2(loc)
         else:
-            self.load_vectors_bin(loc)
+            vec_len = self.load_vectors_bin(loc)
+        return vec_len
 
     def load_vectors_bz2(self, loc):
         cdef LexemeC* lexeme
@@ -278,10 +279,8 @@ cdef class Vocab:
                 if vec_len == -1:
                     vec_len = len(pieces)
                 elif vec_len != len(pieces):
-                    raise IOError(
-                        "Error loading word vectors: all vectors must be same "
-                        "length. Previous vector was length %d, vector on line %d "
-                        "was length %d." % (vec_len, line_num, len(pieces)))
+                    raise VectorReadError.mismatched_sizes(loc, line_num,
+                                                           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))
@@ -293,14 +292,14 @@ cdef class Vocab:
     def load_vectors_bin(self, loc):
         cdef CFile file_ = CFile(loc, b'rb')
         cdef int32_t word_len
-        cdef int32_t vec_len
+        cdef int32_t vec_len = 0
         cdef int32_t prev_vec_len = 0
         cdef float* vec
         cdef Address mem
         cdef attr_t string_id
         cdef bytes py_word
         cdef vector[float*] vectors
-        cdef int i
+        cdef int line_num = 0
         cdef Pool tmp_mem = Pool()
         while True:
             try:
@@ -309,7 +308,8 @@ cdef class Vocab:
                 break
             file_.read_into(&vec_len, sizeof(vec_len), 1)
             if prev_vec_len != 0 and vec_len != prev_vec_len:
-                raise VectorReadError.mismatched_sizes(loc, vec_len, prev_vec_len)
+                raise VectorReadError.mismatched_sizes(loc, line_num,
+                                                       vec_len, prev_vec_len)
             if 0 >= vec_len >= MAX_VEC_SIZE:
                 raise VectorReadError.bad_size(loc, vec_len)
 
@@ -321,8 +321,10 @@ cdef class Vocab:
                 vectors.push_back(EMPTY_VEC)
             assert vec != NULL
             vectors[string_id] = vec
+            line_num += 1
         cdef LexemeC* lex
         cdef size_t lex_addr
+        cdef int i
         for orth, lex_addr in self._by_orth.items():
             lex = <LexemeC*>lex_addr
             if lex.lower < vectors.size():
@@ -363,12 +365,12 @@ def write_binary_vectors(in_loc, out_loc):
 
 class VectorReadError(Exception):
     @classmethod
-    def mismatched_sizes(cls, loc, prev_size, curr_size):
+    def mismatched_sizes(cls, loc, line_num, prev_size, curr_size):
         return cls(
-            "Error reading word vectors from %s.\n"
+            "Error reading word vectors from %s on line %d.\n"
             "All vectors must be the same size.\n"
             "Prev size: %d\n"
-            "Curr size: %d" % (loc, prev_size, curr_size))
+            "Curr size: %d" % (loc, line_num, prev_size, curr_size))
 
     @classmethod
     def bad_size(cls, loc, size):