diff --git a/src/wic/plugins/source/bootimg_efi.py b/src/wic/plugins/source/bootimg_efi.py
index fe6c222..1f73f85 100644
--- a/src/wic/plugins/source/bootimg_efi.py
+++ b/src/wic/plugins/source/bootimg_efi.py
@@ -145,7 +145,8 @@ class BootimgEFIPlugin(SourcePlugin):
         loader_conf = ""
 
         # 5 seconds is a sensible default timeout
-        loader_conf += "timeout %d\n" % (bootloader.timeout or 5)
+        timeout_val = bootloader.timeout if bootloader.timeout is not None else 5
+        loader_conf += f"timeout {timeout_val}\n"
 
         logger.debug("Writing systemd-boot config "
                      "%s/hdd/boot/loader/loader.conf", cr_workdir)