diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/treewalk/filter/IndexDiffFilter.java b/org.eclipse.jgit/src/org/eclipse/jgit/treewalk/filter/IndexDiffFilter.java
index 3ef3d9791..42725bc76 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/treewalk/filter/IndexDiffFilter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/treewalk/filter/IndexDiffFilter.java
@@ -224,7 +224,8 @@ public boolean include(TreeWalk tw) throws MissingObjectException,
 		// Only one chance left to detect a diff: between index and working
 		// tree. Make use of the WorkingTreeIterator#isModified() method to
 		// avoid computing SHA1 on filesystem content if not really needed.
-		return wi.isModified(di.getDirCacheEntry(), true, tw.getObjectReader());
+		return wi.isModified(di == null ? null : di.getDirCacheEntry(), true,
+				tw.getObjectReader());
 	}
 
 	/**