diff --git a/bitbake/lib/toaster/toastermain/settings.py b/bitbake/lib/toaster/toastermain/settings.py
index 3c7cb3bc4d..141ad08877 100644
--- a/bitbake/lib/toaster/toastermain/settings.py
+++ b/bitbake/lib/toaster/toastermain/settings.py
@@ -386,3 +386,10 @@ connection_created.connect(activate_synchronous_off)
 #
 
 
+class InvalidString(str):
+    def __mod__(self, other):
+        from django.template.base import TemplateSyntaxError
+        raise TemplateSyntaxError(
+            "Undefined variable or unknown value for: \"%s\"" % other)
+
+TEMPLATE_STRING_IF_INVALID = InvalidString("%s")