diff --git a/src/osmo_gsm_tester/core/schema.py b/src/osmo_gsm_tester/core/schema.py
index 72c2738..816f439 100644
--- a/src/osmo_gsm_tester/core/schema.py
+++ b/src/osmo_gsm_tester/core/schema.py
@@ -111,7 +111,7 @@
     raise ValueError('Unknown Cipher value: %r' % val)
 
 def modem_feature(val):
-    if val in ('sms', 'gprs', 'voice', 'ussd', 'sim', '2g', '3g', '4g'):
+    if val in ('sms', 'gprs', 'voice', 'ussd', 'sim', '2g', '3g', '4g', 'dl_qam256'):
         return True
     raise ValueError('Unknown Modem Feature: %r' % val)