loude
diff --git a/‎msgpack/_unpacker.pyx
Lines changed: 1 addition & 3 deletions b/‎msgpack/_unpacker.pyx
Lines changed: 1 addition & 3 deletions
diff --git a/‎msgpack/fallback.py
Lines changed: 15 additions & 3 deletions b/‎msgpack/fallback.py
Lines changed: 15 additions & 3 deletions
@@ -113,10 +113,8 @@ def unpackb(object packed, object object_hook=None, object list_hook=None,
         if off < buf_len:
             raise ExtraData(obj, PyBytes_FromStringAndSize(buf+off, buf_len-off))
         return obj
-    elif ret < 0:
-        raise ValueError("Unpack failed: error = %d" % (ret,))
     else:
-        raise UnpackValueError
+        raise UnpackValueError("Unpack failed: error = %d" % (ret,))
 
 
 def unpack(object stream, object object_hook=None, object list_hook=None,
 
@@ -22,6 +22,7 @@ def dict_iteritems(d):
 if hasattr(sys, 'pypy_version_info'):
     # cStringIO is slow on PyPy, StringIO is faster.  However: PyPy's own
     # StringBuilder is fastest.
+    from __pypy__ import newlist_hint
     from __pypy__.builders import StringBuilder
     USING_STRINGBUILDER = True
     class StringIO(object):
@@ -38,6 +39,7 @@ def getvalue(self):
 else:
     USING_STRINGBUILDER = False
     from io import BytesIO as StringIO
+    newlist_hint = lambda size: []
 
 from msgpack.exceptions import (
         BufferFull,
@@ -100,7 +102,10 @@ def unpackb(packed, object_hook=None, list_hook=None, use_list=True,
                         encoding=encoding, unicode_errors=unicode_errors,
                         object_pairs_hook=object_pairs_hook)
     unpacker.feed(packed)
-    ret = unpacker._fb_unpack()
+    try:
+        ret = unpacker._fb_unpack()
+    except OutOfData:
+        raise UnpackValueError("Data is not enough.")
     if unpacker._fb_got_extradata():
         raise ExtraData(ret, unpacker._fb_get_extradata())
     return ret
@@ -266,8 +271,10 @@ def _fb_read(self, n, write_bytes=None):
             write_bytes(ret)
         return ret
 
-    def _fb_unpack(self, execute=EX_CONSTRUCT, write_bytes=None):
+    def _read_header(self, execute=EX_CONSTRUCT, write_bytes=None):
         typ = TYPE_IMMEDIATE
+        n = 0
+        obj = None
         c = self._fb_read(1, write_bytes)
         b = ord(c)
         
B38A
if   b & 0b10000000 == 0:
@@ -341,6 +348,11 @@ def _fb_unpack(self, execute=EX_CONSTRUCT, write_bytes=None):
             typ = TYPE_MAP
         else:
             raise UnpackValueError("Unknown header: 0x%x" % b)
+        return typ, n, obj
+
+    def _fb_unpack(self, execute=EX_CONSTRUCT, write_bytes=None):
+        typ, n, obj = self._read_header(execute, write_bytes)
+
         if execute == EX_CONSTRUCT_SIMPLE:
             if typ in (TYPE_ARRAY, TYPE_MAP):
                 return (typ, n)
@@ -359,7 +371,7 @@ def _fb_unpack(self, execute=EX_CONSTRUCT, write_bytes=None):
                     # TODO check whether we need to call `list_hook`
                     self._fb_unpack(EX_SKIP, write_bytes)
                 return
-            ret = []
+            ret = newlist_hint(n)
             for i in xrange(n):
                 ret.append(self._fb_unpack(EX_CONSTRUCT, write_bytes))
             if self._list_hook is not None: