diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/DiffCommandTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/DiffCommandTest.java
index 16a3d608f..1aa74e891 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/DiffCommandTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/DiffCommandTest.java
@@ -43,6 +43,8 @@
 package org.eclipse.jgit.api;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 
 import java.io.ByteArrayOutputStream;
 import java.io.File;
@@ -222,6 +224,23 @@ public void testDiffWithNegativeLineCount() throws Exception {
 		assertEquals(expected.toString(), actual);
 	}
 
+	@Test
+	public void testNoOutputStreamSet() throws Exception {
+		File file = writeTrashFile("test.txt", "a");
+		assertTrue(file.setLastModified(file.lastModified() - 5000));
+		Git git = new Git(db);
+		git.add().addFilepattern(".").call();
+		write(file, "b");
+
+		List<DiffEntry> diffs = git.diff().call();
+		assertNotNull(diffs);
+		assertEquals(1, diffs.size());
+		DiffEntry diff = diffs.get(0);
+		assertEquals(ChangeType.MODIFY, diff.getChangeType());
+		assertEquals("test.txt", diff.getOldPath());
+		assertEquals("test.txt", diff.getNewPath());
+	}
+
 	private AbstractTreeIterator getTreeIterator(String name)
 			throws IOException {
 		final ObjectId id = db.resolve(name);
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/DiffCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/DiffCommand.java
index 3a50c7a63..e82b0486a 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/DiffCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/DiffCommand.java
@@ -64,6 +64,7 @@
 import org.eclipse.jgit.treewalk.CanonicalTreeParser;
 import org.eclipse.jgit.treewalk.FileTreeIterator;
 import org.eclipse.jgit.treewalk.filter.TreeFilter;
+import org.eclipse.jgit.util.io.NullOutputStream;
 
 /**
  * Show changes between commits, commit and working tree, etc.
@@ -108,8 +109,11 @@ protected DiffCommand(Repository repo) {
 	 * @return a DiffEntry for each path which is different
 	 */
 	public List<DiffEntry> call() throws GitAPIException, IOException {
-		final DiffFormatter diffFmt = new DiffFormatter(
-				new BufferedOutputStream(out));
+		final DiffFormatter diffFmt;
+		if (out != null && !showNameAndStatusOnly)
+			diffFmt = new DiffFormatter(new BufferedOutputStream(out));
+		else
+			diffFmt = new DiffFormatter(NullOutputStream.INSTANCE);
 		diffFmt.setRepository(repo);
 		diffFmt.setProgressMonitor(monitor);
 		try {
@@ -136,17 +140,17 @@ public List<DiffEntry> call() throws GitAPIException, IOException {
 			}
 
 			diffFmt.setPathFilter(pathFilter);
-			if (contextLines >= 0)
-				diffFmt.setContext(contextLines);
-			if (destinationPrefix != null)
-				diffFmt.setNewPrefix(destinationPrefix);
-			if (sourcePrefix != null)
-				diffFmt.setOldPrefix(sourcePrefix);
 
 			List<DiffEntry> result = diffFmt.scan(oldTree, newTree);
-			if (showNameAndStatusOnly) {
+			if (showNameAndStatusOnly)
 				return result;
-			} else {
+			else {
+				if (contextLines >= 0)
+					diffFmt.setContext(contextLines);
+				if (destinationPrefix != null)
+					diffFmt.setNewPrefix(destinationPrefix);
+				if (sourcePrefix != null)
+					diffFmt.setOldPrefix(sourcePrefix);
 				diffFmt.format(result);
 				diffFmt.flush();
 				return result;