diff --git a/metamorph-api/src/main/java/org/metafacture/metamorph/api/helpers/AbstractReadOnlyMap.java b/metamorph-api/src/main/java/org/metafacture/metamorph/api/helpers/AbstractReadOnlyMap.java
index a43ce5054..e3b1ff5d3 100644
--- a/metamorph-api/src/main/java/org/metafacture/metamorph/api/helpers/AbstractReadOnlyMap.java
+++ b/metamorph-api/src/main/java/org/metafacture/metamorph/api/helpers/AbstractReadOnlyMap.java
@@ -29,7 +29,7 @@
  * @param <V> type of values
  * @author Markus Michael Geipel
  */
-public abstract class AbstractReadOnlyMap<K, V> implements Map<K, V> {
+public abstract class AbstractReadOnlyMap<K, V> implements Map<K, V>, AutoCloseable {
 
     @Override
     public final int size() {
diff --git a/metamorph/src/main/java/org/metafacture/metamorph/maps/FileMap.java b/metamorph/src/main/java/org/metafacture/metamorph/maps/FileMap.java
index 8462007ee..26d6c716e 100644
--- a/metamorph/src/main/java/org/metafacture/metamorph/maps/FileMap.java
+++ b/metamorph/src/main/java/org/metafacture/metamorph/maps/FileMap.java
@@ -290,4 +290,9 @@ public Set<String> keySet() {
         return Collections.unmodifiableSet(map.keySet());
     }
 
+    @Override
+    public void close() throws IOException {
+        map.clear();
+        fileOpener.closeStream();
+    }
 }
diff --git a/metamorph/src/main/java/org/metafacture/metamorph/maps/RestMap.java b/metamorph/src/main/java/org/metafacture/metamorph/maps/RestMap.java
index 1a1921947..64692ab10 100644
--- a/metamorph/src/main/java/org/metafacture/metamorph/maps/RestMap.java
+++ b/metamorph/src/main/java/org/metafacture/metamorph/maps/RestMap.java
@@ -107,4 +107,8 @@ public void setCharsetName(final String name) {
         charsetName = name;
     }
 
+    @Override
+    public void close() throws IOException {
+
+    }
 }