diff --git a/querydsl-mongodb/src/main/java/com/mysema/query/mongodb/MongodbSerializer.java b/querydsl-mongodb/src/main/java/com/mysema/query/mongodb/MongodbSerializer.java
index d5a85b24a..5c70da352 100644
--- a/querydsl-mongodb/src/main/java/com/mysema/query/mongodb/MongodbSerializer.java
+++ b/querydsl-mongodb/src/main/java/com/mysema/query/mongodb/MongodbSerializer.java
@@ -20,6 +20,7 @@ import java.util.regex.Pattern;
 import org.bson.BSONObject;
 import org.bson.types.ObjectId;
 
+import com.google.common.collect.Sets;
 import com.mongodb.BasicDBList;
 import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;
@@ -117,9 +118,17 @@ public class MongodbSerializer implements Visitor<Object, Void> {
             return asDBObject(asDBKey(expr, 0), "");
 
         } else if (op == Ops.AND) {
-            BasicDBObject left = (BasicDBObject) handle(expr.getArg(0));
-            left.putAll((BSONObject) handle(expr.getArg(1)));
-            return left;
+            BSONObject lhs = (BSONObject) handle(expr.getArg(0));
+            BSONObject rhs = (BSONObject) handle(expr.getArg(1));
+            if (Sets.intersection(lhs.keySet(), rhs.keySet()).isEmpty()) {
+                lhs.putAll(rhs);
+                return lhs;
+            } else {
+                BasicDBList list = new BasicDBList();
+                list.add(handle(expr.getArg(0)));
+                list.add(handle(expr.getArg(1)));
+                return asDBObject("$and", list);
+            }
 
         } else if (op == Ops.NOT) {
             //Handle the not's child
diff --git a/querydsl-mongodb/src/test/java/com/mysema/query/mongodb/MongodbSerializerTest.java b/querydsl-mongodb/src/test/java/com/mysema/query/mongodb/MongodbSerializerTest.java
index 45923cfde..65d9b80fd 100644
--- a/querydsl-mongodb/src/test/java/com/mysema/query/mongodb/MongodbSerializerTest.java
+++ b/querydsl-mongodb/src/test/java/com/mysema/query/mongodb/MongodbSerializerTest.java
@@ -1,6 +1,6 @@
 /*
  * Copyright 2011, Mysema Ltd
- * 
+ *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
@@ -23,6 +23,7 @@ import java.util.List;
 import org.junit.Before;
 import org.junit.Test;
 
+import com.mongodb.BasicDBList;
 import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;
 import com.mysema.query.mongodb.domain.QDummyEntity;
@@ -141,8 +142,9 @@ public class MongodbSerializerTest {
 
         assertQuery(
                 year.gt(1).and(year.lt(10)),
-                dbo("year", dbo("$gt", 1)).
-                append("year", dbo("$lt", 10))
+                dbo("$and", dblist(
+                  dbo("year", dbo("$gt", 1)),
+                  dbo("year", dbo("$lt", 10))))
         );
 
         assertQuery(
@@ -216,11 +218,16 @@ public class MongodbSerializerTest {
         if (value.length == 1) {
             return new BasicDBObject(key, value[0]);
         }
-
         return new BasicDBObject(key, value);
     }
 
-
+    public static BasicDBList dblist(Object... contents) {
+        BasicDBList list = new BasicDBList();
+        for (Object o : contents) {
+            list.add(o);
+        }
+        return list;
+    }
 
 
 }