diff --git a/datastore_server/source/java/ch/systemsx/cisd/openbis/dss/generic/server/plugins/standard/RsyncArchiveCopierFactory.java b/datastore_server/source/java/ch/systemsx/cisd/openbis/dss/generic/server/plugins/standard/RsyncArchiveCopierFactory.java
index 8a76f64c9d4ca527d7f45b832d345f554f48e7bd..248e6dea508c6c28264c3d3a6c848ba6c9fe8c90 100644
--- a/datastore_server/source/java/ch/systemsx/cisd/openbis/dss/generic/server/plugins/standard/RsyncArchiveCopierFactory.java
+++ b/datastore_server/source/java/ch/systemsx/cisd/openbis/dss/generic/server/plugins/standard/RsyncArchiveCopierFactory.java
@@ -18,6 +18,7 @@ package ch.systemsx.cisd.openbis.dss.generic.server.plugins.standard;
 
 import java.io.File;
 import java.io.Serializable;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
@@ -43,7 +44,8 @@ public final class RsyncArchiveCopierFactory implements Serializable, IPathCopie
     @Override
     public IPathCopier create(File rsyncExecutable, File sshExecutableOrNull, long timeoutInMillis, List<String> additionalCmdLineFlagsOrNull)
     {
-        List<String> additionalCmdLineFlags = Arrays.asList("--archive", "--delete", "--inplace", "--checksum", getTimeoutParameter(timeoutInMillis));
+        List<String> additionalCmdLineFlags = new ArrayList<>(
+                Arrays.asList("--archive", "--delete", "--inplace", "--checksum", getTimeoutParameter(timeoutInMillis)));
         if (additionalCmdLineFlagsOrNull != null)
         {
             additionalCmdLineFlags.addAll(additionalCmdLineFlagsOrNull);
diff --git a/datastore_server/source/java/ch/systemsx/cisd/openbis/dss/generic/server/plugins/standard/RsyncCopierFactory.java b/datastore_server/source/java/ch/systemsx/cisd/openbis/dss/generic/server/plugins/standard/RsyncCopierFactory.java
index ce99c65af6e99b91e520dcadea464387fce97ad8..866eedefa2668efef8bbeb15c740dd9791cbf2df 100644
--- a/datastore_server/source/java/ch/systemsx/cisd/openbis/dss/generic/server/plugins/standard/RsyncCopierFactory.java
+++ b/datastore_server/source/java/ch/systemsx/cisd/openbis/dss/generic/server/plugins/standard/RsyncCopierFactory.java
@@ -28,8 +28,15 @@ public final class RsyncCopierFactory implements Serializable, IPathCopierFactor
     private static final long serialVersionUID = 1L;
 
     @Override
-    public IPathCopier create(File rsyncExecutable, File sshExecutableOrNull, long timeoutInMillis, List<String> additionalCmdLineFlagsOrNull)
+    public IPathCopier create(File rsyncExecutable, File sshExecutableOrNull, long timeoutInMillis, 
+            List<String> additionalCmdLineFlagsOrNull)
     {
-        return new RsyncCopier(rsyncExecutable, sshExecutableOrNull, false, false, additionalCmdLineFlagsOrNull.toArray(new String[0]));
+        String[] additionalCmdLineFlags = new String[0];
+        if (additionalCmdLineFlagsOrNull != null)
+        {
+            additionalCmdLineFlags = additionalCmdLineFlagsOrNull.toArray(new String[0]);
+        }
+        return new RsyncCopier(rsyncExecutable, sshExecutableOrNull, false, false, 
+                additionalCmdLineFlags);
     }
 }
\ No newline at end of file