diff --git a/gns3server/compute/virtualbox/__init__.py b/gns3server/compute/virtualbox/__init__.py
index 3b716bb9..fcf40ea3 100644
--- a/gns3server/compute/virtualbox/__init__.py
+++ b/gns3server/compute/virtualbox/__init__.py
@@ -68,7 +68,7 @@ class VirtualBox(BaseManager):
             else:
                 vboxmanage_path = "vboxmanage"
 
-        if not os.path.isabs(vboxmanage_path):
+        if vboxmanage_path and not os.path.isabs(vboxmanage_path):
             vboxmanage_path = shutil.which(vboxmanage_path)
 
         if not vboxmanage_path: