diff --git a/pom.xml b/pom.xml
index 7ece8d34f79..75476e3595a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -129,6 +129,9 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
+                <configuration>
+                    <source>${java.version}</source>
+                </configuration>
                 <executions>
                     <execution>
                         <id>attach-javadocs</id>
diff --git a/spring-boot-admin-server/src/main/java/de/codecentric/boot/admin/server/domain/values/Registration.java b/spring-boot-admin-server/src/main/java/de/codecentric/boot/admin/server/domain/values/Registration.java
index e41bafc08f6..48c2f3e6be7 100644
--- a/spring-boot-admin-server/src/main/java/de/codecentric/boot/admin/server/domain/values/Registration.java
+++ b/spring-boot-admin-server/src/main/java/de/codecentric/boot/admin/server/domain/values/Registration.java
@@ -82,7 +82,7 @@ public static Registration.Builder copyOf(Registration registration) {
     }
 
     public Map<String, String> getMetadata() {
-        return Collections.unmodifiableMap(metadata);
+        return Collections.unmodifiableMap(this.metadata);
     }
 
     /**