diff --git a/src/java/org/apache/poi/poifs/filesystem/NPOIFSFileSystem.java b/src/java/org/apache/poi/poifs/filesystem/NPOIFSFileSystem.java
index b15df9bd4..8b2f9e9ea 100644
--- a/src/java/org/apache/poi/poifs/filesystem/NPOIFSFileSystem.java
+++ b/src/java/org/apache/poi/poifs/filesystem/NPOIFSFileSystem.java
@@ -19,6 +19,7 @@
 
 package org.apache.poi.poifs.filesystem;
 
+import java.io.Closeable;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
@@ -64,7 +65,7 @@ import org.apache.poi.util.POILogger;
  */
 
 public class NPOIFSFileSystem extends BlockStore
-    implements POIFSViewable
+    implements POIFSViewable, Closeable
 {
 	private static final POILogger _logger =
 		POILogFactory.getLogger(NPOIFSFileSystem.class);
diff --git a/src/ooxml/java/org/apache/poi/openxml4j/opc/OPCPackage.java b/src/ooxml/java/org/apache/poi/openxml4j/opc/OPCPackage.java
index 8be4fa9f1..a031a5f66 100644
--- a/src/ooxml/java/org/apache/poi/openxml4j/opc/OPCPackage.java
+++ b/src/ooxml/java/org/apache/poi/openxml4j/opc/OPCPackage.java
@@ -18,6 +18,7 @@
 package org.apache.poi.openxml4j.opc;
 
 import java.io.ByteArrayOutputStream;
+import java.io.Closeable;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
@@ -56,7 +57,7 @@ import org.apache.poi.util.POILogFactory;
  * @author Julien Chable, CDubet
  * @version 0.1
  */
-public abstract class OPCPackage implements RelationshipSource {
+public abstract class OPCPackage implements RelationshipSource, Closeable {
 
 	/**
 	 * Logger.