diff --git a/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/xls/importer/delay/DelayedExecution.java b/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/xls/importer/delay/DelayedExecution.java
index 53ad6a53d9766f593f961704ff91df28e42da6e4..77ae11c0b936a9202f2c0a78fef2bc0f4ba3f9f9 100644
--- a/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/xls/importer/delay/DelayedExecution.java
+++ b/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/xls/importer/delay/DelayedExecution.java
@@ -64,7 +64,9 @@ public class DelayedExecution
             return false;
         }
         DelayedExecution that = (DelayedExecution) o;
-        return creationOrUpdate.getClass() == that.creationOrUpdate.getClass() && identifier.equals(that.identifier);
+        return creationOrUpdate.getClass() == that.creationOrUpdate.getClass() &&
+                identifier != null &&
+                identifier.equals(that.identifier);
     }
 
     @Override