diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackWriter.java b/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackWriter.java
index df5594cf4..1bb11c3a0 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackWriter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackWriter.java
@@ -487,6 +487,7 @@ public void writePack(ProgressMonitor compressMonitor,
 		int objCnt = getObjectsNumber();
 		writeMonitor.beginTask(JGitText.get().writingObjects, objCnt);
 		out.writeFileHeader(PACK_VERSION_GENERATED, objCnt);
+		out.flush();
 		writeObjects(writeMonitor, out);
 		writeChecksum(out);