diff --git a/bson/__init__.py b/bson/__init__.py
index e89a7114f..38e2009d0 100644
--- a/bson/__init__.py
+++ b/bson/__init__.py
@@ -311,9 +311,10 @@ def _elements_to_dict(data, as_class, tz_aware):
 
 def _bson_to_dict(data, as_class, tz_aware):
     obj_size = struct.unpack("<i", data[:4])[0]
-    if len(data) < obj_size:
+    length = len(data)
+    if length < obj_size:
         raise InvalidBSON("objsize too large")
-    if data[obj_size - 1:obj_size] != ZERO:
+    if obj_size != length or data[obj_size - 1:obj_size] != ZERO:
         raise InvalidBSON("bad eoo")
     elements = data[4:obj_size - 1]
     return (_elements_to_dict(elements, as_class, tz_aware), data[obj_size:])
@@ -572,4 +573,4 @@ def has_uuid():
 
     .. versionadded:: 2.2.1+
     """
-    return _use_uuid
\ No newline at end of file
+    return _use_uuid
diff --git a/bson/_cbsonmodule.c b/bson/_cbsonmodule.c
index d912524f4..aee64fbb5 100644
--- a/bson/_cbsonmodule.c
+++ b/bson/_cbsonmodule.c
@@ -1628,7 +1628,7 @@ static PyObject* _cbson_bson_to_dict(PyObject* self, PyObject* args) {
         return NULL;
     }
 
-    if (string[size - 1]) {
+    if (size != total_size || string[size - 1]) {
         PyObject* InvalidBSON = _error("InvalidBSON");
         PyErr_SetString(InvalidBSON,
                         "bad eoo");
diff --git a/test/test_bson.py b/test/test_bson.py
index e8d63555a..5ffb03ed9 100644
--- a/test/test_bson.py
+++ b/test/test_bson.py
@@ -74,6 +74,7 @@ class TestBSON(unittest.TestCase):
         self.assertFalse(is_valid(b("\x05\x00\x00\x00\x00\x00")))
         self.assertFalse(is_valid(b("\x07\x00\x00\x00\x02a\x00\x78\x56\x34\x12")))
         self.assertFalse(is_valid(b("\x09\x00\x00\x00\x10a\x00\x05\x00")))
+        self.assertFalse(is_valid(b("\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00")))
 
     def test_random_data_is_not_bson(self):
         qcheck.check_unittest(self, qcheck.isnt(is_valid),