diff --git a/src/pylorax/installer.py b/src/pylorax/installer.py
index 6317c571..85a335df 100644
--- a/src/pylorax/installer.py
+++ b/src/pylorax/installer.py
@@ -566,7 +566,7 @@ def virt_install(opts, install_log, disk_img, disk_size, cancel_func=None):
         else:
             msg = "virt_install failed on line: %s" % log_monitor.server.error_line
         raise InstallError(msg)
-    elif cancel_func():
+    elif cancel_func and cancel_func():
         raise InstallError("virt_install canceled by cancel_func")
 
     if opts.make_fsimage: