diff --git a/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/MessageHeaderPropagation.java b/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/MessageHeaderPropagation.java
index 13ec0e0f8..4d0fffa9c 100644
--- a/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/MessageHeaderPropagation.java
+++ b/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/MessageHeaderPropagation.java
@@ -151,11 +151,18 @@ enum MessageHeaderPropagation
 						nativeHeaders);
 			}
 			if (nativeHeaders instanceof Map<?, ?>) {
-				((Map) nativeHeaders).put(key, Collections.singletonList(value));
+				Map<String, List<String>> copy = toNativeHeaderMap(
+						(Map<String, List<String>>) nativeHeaders);
+				copy.put(key, Collections.singletonList(value));
+				accessor.setHeader(NativeMessageHeaderAccessor.NATIVE_HEADERS, copy);
 			}
 		}
 	}
 
+	private Map<String, List<String>> toNativeHeaderMap(Map<String, List<String>> map) {
+		return (map != null ? new LinkedMultiValueMap<>(map) : Collections.emptyMap());
+	}
+
 	@Override
 	public String get(MessageHeaderAccessor accessor, String key) {
 		try {