diff --git a/lib/bson/parser/serializer.js b/lib/bson/parser/serializer.js
index e4ff2bd9..6bb212ed 100644
--- a/lib/bson/parser/serializer.js
+++ b/lib/bson/parser/serializer.js
@@ -777,6 +777,8 @@ var serializeInto = function serializeInto(
         index = serializeInt32(buffer, key, value, index, true);
       } else if (value['_bsontype'] === 'MinKey' || value['_bsontype'] === 'MaxKey') {
         index = serializeMinMax(buffer, key, value, index, true);
+      } else if (typeof value['_bsontype'] !== 'undefined') {
+        throw new TypeError('Unrecognized or invalid _bsontype: ' + value['_bsontype']);
       }
     }
   } else if (object instanceof Map) {
@@ -875,6 +877,8 @@ var serializeInto = function serializeInto(
         index = serializeInt32(buffer, key, value, index);
       } else if (value['_bsontype'] === 'MinKey' || value['_bsontype'] === 'MaxKey') {
         index = serializeMinMax(buffer, key, value, index);
+      } else if (typeof value['_bsontype'] !== 'undefined') {
+        throw new TypeError('Unrecognized or invalid _bsontype: ' + value['_bsontype']);
       }
     }
   } else {
@@ -977,6 +981,8 @@ var serializeInto = function serializeInto(
         index = serializeInt32(buffer, key, value, index);
       } else if (value['_bsontype'] === 'MinKey' || value['_bsontype'] === 'MaxKey') {
         index = serializeMinMax(buffer, key, value, index);
+      } else if (typeof value['_bsontype'] !== 'undefined') {
+        throw new TypeError('Unrecognized or invalid _bsontype: ' + value['_bsontype']);
       }
     }
   }
diff --git a/test/node/bson_test.js b/test/node/bson_test.js
index 5c948df2..6bce9b01 100644
--- a/test/node/bson_test.js
+++ b/test/node/bson_test.js
@@ -21,6 +21,7 @@ var Buffer = require('buffer').Buffer,
   vm = require('vm');
 
 var createBSON = require('../utils');
+var M = require('../../lib/bson/map');
 
 // for tests
 BSON.BSON_BINARY_SUBTYPE_DEFAULT = 0;
@@ -2400,3 +2401,23 @@ exports['Should serialize _bsontype=ObjectID (capital D) from v4.0.0/4.0.1'] = f
   test.equal(doc._id.toHexString(), createBSON().deserialize(serialized_data)._id.toHexString());
   test.done();
 };
+
+exports['should throw if invalid BSON types are input to BSON serializer'] = function(test) {
+  var oid = new ObjectId('111111111111111111111111');
+  var badBsonType = new ObjectId('111111111111111111111111');
+  badBsonType._bsontype = 'bogus';
+  var badDoc = { bad: badBsonType };
+  var badArray = [oid, badDoc];
+  var badMap = new M([['a', badBsonType], ['b', badDoc], ['c', badArray]]);
+  var BSON = createBSON();
+  test.throws(function() {
+    BSON.serialize(badDoc);
+  });
+  test.throws(function() {
+    BSON.serialize(badArray);
+  });
+  test.throws(function() {
+    BSON.serialize(badMap);
+  });
+  test.done();
+}