diff --git a/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/MilliSpan.java b/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/MilliSpan.java
index cc0a2061c..dd0b18a6e 100644
--- a/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/MilliSpan.java
+++ b/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/MilliSpan.java
@@ -17,6 +17,7 @@
 package org.springframework.cloud.sleuth;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -104,4 +105,9 @@ public class MilliSpan implements Span {
 				msg));
 	}
 
+	@Override
+	public Map<String, String> getAnnotations() {
+		return Collections.unmodifiableMap(kVAnnotations);
+	}
+
 }
diff --git a/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/MilliSpanTests.java b/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/MilliSpanTests.java
new file mode 100644
index 000000000..91fc45885
--- /dev/null
+++ b/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/MilliSpanTests.java
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2013-2015 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.sleuth;
+
+import java.util.Collections;
+
+import org.junit.Test;
+
+/**
+ * @author Rob Winch
+ */
+public class MilliSpanTests {
+
+
+	@Test(expected = UnsupportedOperationException.class)
+	public void getAnnotationsReadOnly() {
+		MilliSpan span = new MilliSpan(1, 2, "name", "traceId", Collections.<String>emptyList(), "spanId", true, "processId");
+
+		span.getAnnotations().put("a", "b");
+	}
+}
\ No newline at end of file