diff --git a/osrepodbmgr.Core/ChangeLog b/osrepodbmgr.Core/ChangeLog
index 527543f..538ec4d 100644
--- a/osrepodbmgr.Core/ChangeLog
+++ b/osrepodbmgr.Core/ChangeLog
@@ -1,3 +1,8 @@
+2017-05-11  Natalia Portillo  <claunia@claunia.com>
+
+	* Workers.cs:
+	  Use DotNetZip to test for ZIP file.
+
 2017-05-11  Natalia Portillo  <claunia@claunia.com>
 
 	* Workers.cs:
diff --git a/osrepodbmgr.Core/Workers.cs b/osrepodbmgr.Core/Workers.cs
index 2c448e1..524fd10 100644
--- a/osrepodbmgr.Core/Workers.cs
+++ b/osrepodbmgr.Core/Workers.cs
@@ -1105,7 +1105,7 @@ namespace osrepodbmgr.Core
                     return;
                 }
 
-                if(format == "Zip")
+                if(ZipFile.IsZipFile(Context.path))
                 {
                     Context.copyArchive = true;
                     ZipFile zf = ZipFile.Read(Context.path);