diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/query/Update.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/query/Update.java
index 948297c7a..0e34141d9 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/query/Update.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/query/Update.java
@@ -372,7 +372,7 @@ public class Update {
 	 */
 	@Override
 	public String toString() {
-		return getUpdateObject().toString();
+		return SerializationUtils.serializeToJsonSafely(getUpdateObject());
 	}
 
 	/**
diff --git a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/query/UpdateTests.java b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/query/UpdateTests.java
index b8454c770..7cec115d6 100644
--- a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/query/UpdateTests.java
+++ b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/query/UpdateTests.java
@@ -21,6 +21,7 @@ import static org.junit.Assert.*;
 import java.util.Collections;
 import java.util.Map;
 
+import org.joda.time.DateTime;
 import org.junit.Test;
 
 /**
@@ -342,4 +343,14 @@ public class UpdateTests {
 				+ "\"$push\" : { \"authors\" : { \"name\" : \"Sven\"}} " //
 				+ ", \"$pop\" : { \"authors\" : -1}}")); //
 	}
+
+	/**
+	 * @see DATAMONGO-1002
+	 */
+	@Test
+	public void toStringWorksForUpdateWithComplexObject() {
+
+		Update update = new Update().addToSet("key", new DateTime());
+		assertThat(update.toString(), is(notNullValue()));
+	}
 }