diff --git a/main/src/com/google/refine/importing/ImportingManager.java b/main/src/com/google/refine/importing/ImportingManager.java
index 35e0bb1ea..9cbd2fc6d 100644
--- a/main/src/com/google/refine/importing/ImportingManager.java
+++ b/main/src/com/google/refine/importing/ImportingManager.java
@@ -44,6 +44,7 @@ import java.util.Properties;
 import java.util.Set;
 import java.util.Timer;
 import java.util.TimerTask;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.io.FileUtils;
 import org.json.JSONException;
@@ -82,7 +83,7 @@ public class ImportingManager {
     
     static private RefineServlet servlet;
     static private File importDir;
-    final static private Map<Long, ImportingJob> jobs = new HashMap<Long, ImportingJob>();
+    final static private Map<Long, ImportingJob> jobs = new ConcurrentHashMap<Long, ImportingJob>();
     
     // Mapping from format to label, e.g., "text" to "Text files", "text/xml" to "XML files"
     final static public Map<String, Format> formatToRecord = new HashMap<String, Format>();
@@ -288,12 +289,11 @@ public class ImportingManager {
     
     static private void cleanUpStaleJobs() {
         long now = System.currentTimeMillis();
-        for (Long id : new HashSet<Long>(jobs.keySet())) {
+        for (Long id : jobs.keySet()) {
             ImportingJob job = jobs.get(id);
             if (job != null && !job.updating && now - job.lastTouched > s_stalePeriod) {
                 job.dispose();
                 jobs.remove(id);
-                
                 logger.info("Disposed " + id);
             }
         }