diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ExposedFieldsAggregationOperationContext.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ExposedFieldsAggregationOperationContext.java
index 88590bed8..ca7d8db5b 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ExposedFieldsAggregationOperationContext.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ExposedFieldsAggregationOperationContext.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 the original author or authors.
+ * Copyright 2013-2014 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -69,12 +69,26 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 	@Override
 	public FieldReference getReference(String name) {
 
+		Assert.notNull(name, "Name must not be null!");
+
 		ExposedField field = exposedFields.getField(name);
 
 		if (field != null) {
 			return new FieldReference(field);
 		}
 
+		if (name.contains(".")) {
+
+			// for nested field references we only check that the root field exists.
+			ExposedField rootField = exposedFields.getField(name.split("\\.")[0]);
+
+			if (rootField != null) {
+
+				// We have to synthetic to true, in order to render the field-name as is.
+				return new FieldReference(new ExposedField(name, true));
+			}
+		}
+
 		throw new IllegalArgumentException(String.format("Invalid reference '%s'!", name));
 	}
 }
diff --git a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/AggregationUnitTests.java b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/AggregationUnitTests.java
index dae68fda1..2012200e6 100644
--- a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/AggregationUnitTests.java
+++ b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/AggregationUnitTests.java
@@ -179,4 +179,25 @@ public class AggregationUnitTests {
 		DBObject fields = getAsDBObject(secondProjection, "$group");
 		assertThat(fields.get("foosum"), is((Object) new BasicDBObject("$sum", "$foo")));
 	}
+
+	/**
+	 * @see DATAMONGO-908
+	 */
+	@Test
+	public void shouldSupportReferingToNestedPropertiesInGroupOperation() {
+
+		DBObject agg = newAggregation( //
+				project("cmsParameterId", "rules"), //
+				unwind("rules"), //
+				group("cmsParameterId", "rules.ruleType").count().as("totol") //
+		).toDbObject("foo", Aggregation.DEFAULT_CONTEXT);
+
+		assertThat(agg, is(notNullValue()));
+
+		DBObject group = ((List<DBObject>) agg.get("pipeline")).get(2);
+		DBObject fields = getAsDBObject(group, "$group");
+		DBObject id = getAsDBObject(fields, "_id");
+
+		assertThat(id.get("ruleType"), is((Object) "$rules.ruleType"));
+	}
 }