diff --git a/spring-integration-core/src/main/java/org/springframework/integration/message/HeaderMapper.java b/spring-integration-core/src/main/java/org/springframework/integration/message/HeaderMapper.java
index a46a467bbb..c534131b75 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/message/HeaderMapper.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/message/HeaderMapper.java
@@ -33,6 +33,6 @@ public interface HeaderMapper<T> {
 
 	void fromHeaders(MessageHeaders headers, T target);
 
-	Map<String, Object> toHeaders(T source);
+	Map<String, ?> toHeaders(T source);
 
 }