diff --git a/bson/__init__.py b/bson/__init__.py
index 07999c085..605ea5833 100644
--- a/bson/__init__.py
+++ b/bson/__init__.py
@@ -93,7 +93,15 @@ BSONMAX = b("\x7F") # Max key
 _CODEC_OPTIONS_TYPE_ERROR = TypeError(
     "codec_options must be an instance of bson.codec_options.CodecOptions")
 
-def _get_int(data, position, as_class=None,
+
+def _raise_unknown_type(element_type, element_name):
+    """Unknown type helper."""
+    raise InvalidBSON("Detected unknown BSON type %r for fieldname %r. Are "
+                      "you using the latest driver version?" % (
+                          element_type, element_name))
+
+
+def _get_int(data, position, name, as_class=None,
              tz_aware=False, uuid_subtype=OLD_UUID_SUBTYPE,
              compile_re=True, unsigned=False):
     format = unsigned and "I" or "i"
@@ -137,13 +145,15 @@ def _make_c_string(string, check_null=False):
                                     "UTF-8: %r" % string)
 
 
-def _get_number(data, position, as_class, tz_aware, uuid_subtype, compile_re):
+def _get_number(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
     num = struct.unpack("<d", data[position:position + 8])[0]
     position += 8
     return num, position
 
 
-def _get_string(data, position, as_class, tz_aware, uuid_subtype, compile_re):
+def _get_string(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
     length = struct.unpack("<i", data[position:position + 4])[0]
     if length <= 0 or (len(data) - position - 4) < length:
         raise InvalidBSON("invalid string length")
@@ -153,7 +163,8 @@ def _get_string(data, position, as_class, tz_aware, uuid_subtype, compile_re):
     return _get_c_string(data, position, length - 1)
 
 
-def _get_object(data, position, as_class, tz_aware, uuid_subtype, compile_re):
+def _get_object(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
     obj_size = struct.unpack("<i", data[position:position + 4])[0]
     if data[position + obj_size - 1:position + obj_size] != ZERO:
         raise InvalidBSON("bad eoo")
@@ -168,26 +179,43 @@ def _get_object(data, position, as_class, tz_aware, uuid_subtype, compile_re):
     return object, position
 
 
-def _get_array(data, position, as_class, tz_aware, uuid_subtype, compile_re):
-    obj, position = _get_object(data, position,
-                                as_class, tz_aware, uuid_subtype, compile_re)
+def _get_array(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
+    size = struct.unpack("<i", data[position:position + 4])[0]
+    end = position + size - 1
+    if data[end:end + 1] != ZERO:
+        raise InvalidBSON("bad eoo")
+
+    position += 4
+    end -= 1
     result = []
-    i = 0
-    while True:
+
+    # Avoid doing global and attibute lookups in the loop.
+    append = result.append
+    index = data.index
+    getter = _element_getter
+
+    while position < end:
+        element_type = data[position:position + 1]
+        # Just skip the keys.
+        position = index(ZERO, position) + 1
         try:
-            result.append(obj[str(i)])
-            i += 1
+            value, position = getter[element_type](
+                data, position, name,
+                as_class, tz_aware, uuid_subtype, compile_re)
         except KeyError:
-            break
-    return result, position
+            _raise_unknown_type(element_type, name)
+        append(value)
+    return result, position + 1
 
 
-def _get_binary(data, position, as_class, tz_aware, uuid_subtype, compile_re):
-    length, position = _get_int(data, position)
+def _get_binary(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
+    length, position = _get_int(data, position, name)
     subtype = ord(data[position:position + 1])
     position += 1
     if subtype == 2:
-        length2, position = _get_int(data, position)
+        length2, position = _get_int(data, position, name)
         if length2 != length - 4:
             raise InvalidBSON("invalid binary (st 2) - lengths don't match!")
         length = length2
@@ -213,20 +241,22 @@ def _get_binary(data, position, as_class, tz_aware, uuid_subtype, compile_re):
     return value, position
 
 
-def _get_oid(data, position, as_class=None,
+def _get_oid(data, position, name, as_class=None,
              tz_aware=False, uuid_subtype=OLD_UUID_SUBTYPE, compile_re=True):
     value = ObjectId(data[position:position + 12])
     position += 12
     return value, position
 
 
-def _get_boolean(data, position, as_class, tz_aware, uuid_subtype, compile_re):
+def _get_boolean(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
     value = data[position:position + 1] == ONE
     position += 1
     return value, position
 
 
-def _get_date(data, position, as_class, tz_aware, uuid_subtype, compile_re):
+def _get_date(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
     millis = struct.unpack("<q", data[position:position + 8])[0]
     diff = millis % 1000
     seconds = (millis - diff) / 1000
@@ -238,27 +268,30 @@ def _get_date(data, position, as_class, tz_aware, uuid_subtype, compile_re):
     return dt.replace(microsecond=diff * 1000), position
 
 
-def _get_code(data, position, as_class, tz_aware, uuid_subtype, compile_re):
-    code, position = _get_string(data, position,
+def _get_code(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
+    code, position = _get_string(data, position, name,
                                  as_class, tz_aware, uuid_subtype, compile_re)
     return Code(code), position
 
 
 def _get_code_w_scope(
-        data, position, as_class, tz_aware, uuid_subtype, compile_re):
-    _, position = _get_int(data, position)
-    code, position = _get_string(data, position,
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
+    _, position = _get_int(data, position, name)
+    code, position = _get_string(data, position, name,
                                  as_class, tz_aware, uuid_subtype, compile_re)
-    scope, position = _get_object(data, position,
+    scope, position = _get_object(data, position, name,
                                   as_class, tz_aware, uuid_subtype, compile_re)
     return Code(code, scope), position
 
 
-def _get_null(data, position, as_class, tz_aware, uuid_subtype, compile_re):
+def _get_null(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
     return None, position
 
 
-def _get_regex(data, position, as_class, tz_aware, uuid_subtype, compile_re):
+def _get_regex(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
     pattern, position = _get_c_string(data, position)
     bson_flags, position = _get_c_string(data, position)
     bson_re = Regex(pattern, bson_flags)
@@ -268,21 +301,23 @@ def _get_regex(data, position, as_class, tz_aware, uuid_subtype, compile_re):
         return bson_re, position
 
 
-def _get_ref(data, position, as_class, tz_aware, uuid_subtype, compile_re):
-    collection, position = _get_string(data, position, as_class, tz_aware,
-                                       uuid_subtype, compile_re)
-    oid, position = _get_oid(data, position)
+def _get_ref(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
+    collection, position = _get_string(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re)
+    oid, position = _get_oid(data, position, name)
     return DBRef(collection, oid), position
 
 
 def _get_timestamp(
-        data, position, as_class, tz_aware, uuid_subtype, compile_re):
-    inc, position = _get_int(data, position, unsigned=True)
-    timestamp, position = _get_int(data, position, unsigned=True)
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
+    inc, position = _get_int(data, position, name, unsigned=True)
+    timestamp, position = _get_int(data, position, name, unsigned=True)
     return Timestamp(timestamp, inc), position
 
 
-def _get_long(data, position, as_class, tz_aware, uuid_subtype, compile_re):
+def _get_long(
+        data, position, name, as_class, tz_aware, uuid_subtype, compile_re):
     # Have to cast to long; on 32-bit unpack may return an int.
     # 2to3 will change long to int. That's fine since long doesn't
     # exist in python3.
@@ -310,8 +345,8 @@ _element_getter = {
     BSONINT: _get_int,  # number_int
     BSONTIM: _get_timestamp,
     BSONLON: _get_long, # Same as _get_int after 2to3 runs.
-    BSONMIN: lambda u, v, w, x, y, z: (MinKey(), v),
-    BSONMAX: lambda u, v, w, x, y, z: (MaxKey(), v)}
+    BSONMIN: lambda t, u, v, w, x, y, z: (MinKey(), u),
+    BSONMAX: lambda t, u, v, w, x, y, z: (MaxKey(), u)}
 
 
 def _element_to_dict(
@@ -319,8 +354,12 @@ def _element_to_dict(
     element_type = data[position:position + 1]
     position += 1
     element_name, position = _get_c_string(data, position)
-    value, position = _element_getter[element_type](
-        data, position, as_class, tz_aware, uuid_subtype, compile_re)
+    try:
+        func = _element_getter[element_type]
+    except KeyError:
+        _raise_unknown_type(element_type, element_name)
+    value, position = func(data, position, element_name,
+                           as_class, tz_aware, uuid_subtype, compile_re)
 
     return element_name, value, position
 
diff --git a/bson/_cbsonmodule.c b/bson/_cbsonmodule.c
index 350c35d98..81d8d0d21 100644
--- a/bson/_cbsonmodule.c
+++ b/bson/_cbsonmodule.c
@@ -1427,10 +1427,10 @@ static PyObject* _cbson_dict_to_bson(PyObject* self, PyObject* args) {
     return result;
 }
 
-static PyObject* get_value(PyObject* self, const char* buffer, unsigned* position,
-                           unsigned char type, unsigned max, PyObject* as_class,
-                           unsigned char tz_aware, unsigned char uuid_subtype,
-                           unsigned char compile_re) {
+static PyObject* get_value(PyObject* self, PyObject* name, const char* buffer,
+                           unsigned* position, unsigned char type, unsigned max,
+                           PyObject* as_class, unsigned char tz_aware,
+                           unsigned char uuid_subtype, unsigned char compile_re) {
     struct module_state *state = GETSTATE(self);
 
     PyObject* value = NULL;
@@ -1574,7 +1574,7 @@ static PyObject* get_value(PyObject* self, const char* buffer, unsigned* positio
                     Py_DECREF(value);
                     goto invalid;
                 }
-                to_append = get_value(self, buffer, position, bson_type,
+                to_append = get_value(self, name, buffer, position, bson_type,
                                       max - (unsigned)key_size,
                                       as_class, tz_aware, uuid_subtype,
                                       compile_re);
@@ -2078,11 +2078,50 @@ static PyObject* get_value(PyObject* self, const char* buffer, unsigned* positio
         }
     default:
         {
-            PyObject* InvalidDocument = _error("InvalidDocument");
-            if (InvalidDocument) {
-                PyErr_SetString(InvalidDocument,
-                                "no c decoder for this type yet");
-                Py_DECREF(InvalidDocument);
+            PyObject* InvalidBSON = _error("InvalidBSON");
+            if (InvalidBSON) {
+#if PY_MAJOR_VERSION >= 3
+                PyObject* type_obj = PyBytes_FromFormat("%c", type);
+#else
+                PyObject* type_obj = PyString_FromFormat("%c", type);
+#endif
+                if (type_obj) {
+                    PyObject* type_repr = PyObject_Repr(type_obj);
+                    Py_DECREF(type_obj);
+                    if (type_repr) {
+                        PyObject* errmsg = NULL;
+#if PY_MAJOR_VERSION >= 3
+                        PyObject* left = PyUnicode_FromString(
+                            "Detected unknown BSON type ");
+                        if (left) {
+                            PyObject* lmsg = PyUnicode_Concat(left, type_repr);
+                            Py_DECREF(left);
+                            if (lmsg) {
+                                errmsg = PyUnicode_FromFormat(
+                                    "%U for fieldname '%U'. Are you using the "
+                                    "latest driver version?", lmsg, name);
+                                Py_DECREF(lmsg);
+                            }
+                        }
+#else
+                        PyObject* name_repr = PyObject_Repr(name);
+                        if (name_repr) {
+                            errmsg = PyString_FromFormat(
+                                "Detected unknown BSON type %s for fieldname %s."
+                                " Are you using the latest driver version?",
+                                PyString_AS_STRING(type_repr),
+                                PyString_AS_STRING(name_repr));
+                            Py_DECREF(name_repr);
+                        }
+#endif
+                        Py_DECREF(type_repr);
+                        if (errmsg) {
+                            PyErr_SetObject(InvalidBSON, errmsg);
+                            Py_DECREF(errmsg);
+                        }
+                    }
+                }
+                Py_DECREF(InvalidBSON);
             }
             goto invalid;
         }
@@ -2173,7 +2212,7 @@ static PyObject* _elements_to_dict(PyObject* self, const char* string,
             return NULL;
         }
         position += (unsigned)name_length + 1;
-        value = get_value(self, string, &position, type,
+        value = get_value(self, name, string, &position, type,
                           max - position, as_class, tz_aware, uuid_subtype,
                           compile_re);
         if (!value) {
diff --git a/test/test_bson.py b/test/test_bson.py
index 1985b5fd6..d87faf5ba 100644
--- a/test/test_bson.py
+++ b/test/test_bson.py
@@ -358,6 +358,24 @@ class TestBSON(unittest.TestCase):
         qcheck.check_unittest(self, encode_then_decode_backport_precedence,
                               qcheck.gen_mongo_dict(3))
 
+    def test_unknown_type(self):
+        # Repr value differs with major python version
+        part = "type %r for fieldname %r" % (b('\x13'), u"foo")
+        docs = [
+            b('\x0e\x00\x00\x00\x13foo\x00\x01\x00\x00\x00\x00'),
+            b('\x16\x00\x00\x00\x04foo\x00\x0c\x00\x00\x00\x130'
+              '\x00\x01\x00\x00\x00\x00\x00'),
+            b(' \x00\x00\x00\x04bar\x00\x16\x00\x00\x00\x030\x00\x0e\x00\x00'
+              '\x00\x13foo\x00\x01\x00\x00\x00\x00\x00\x00')]
+        for bs in docs:
+            try:
+                bson.BSON(bs).decode()
+            except Exception, exc:
+                self.assertTrue(isinstance(exc, InvalidBSON))
+                self.assertTrue(part in str(exc))
+            else:
+                self.fail("Failed to raise an exception.")
+
     def test_dbpointer(self):
         # *Note* - DBPointer and DBRef are *not* the same thing. DBPointer
         # is a deprecated BSON type. DBRef is a convention that does not