diff --git a/pmb/flasher/run.py b/pmb/flasher/run.py
index a8d758ee..a7cce7e8 100644
--- a/pmb/flasher/run.py
+++ b/pmb/flasher/run.py
@@ -48,7 +48,7 @@ def run(args, action, flavor=None):
         for key, value in vars.items():
             for i in range(len(command)):
                 if key in command[i]:
-                    if not value and key != "$KERNEL_CMDLINE":
+                    if value is None:
                         raise RuntimeError("Variable " + key + " found in"
                                            " action " + action + " for method " + method + ","
                                            " but the value for this variable is None! Is that"
diff --git a/pmb/flasher/variables.py b/pmb/flasher/variables.py
index a63db0cf..eb36f91a 100644
--- a/pmb/flasher/variables.py
+++ b/pmb/flasher/variables.py
@@ -3,7 +3,7 @@
 
 
 def variables(args, flavor, method):
-    _cmdline = args.deviceinfo["kernel_cmdline"]
+    _cmdline = args.deviceinfo["kernel_cmdline"] or ""
     if "cmdline" in args and args.cmdline:
         _cmdline = args.cmdline