diff --git a/src/osmo_gsm_tester/resource.py b/src/osmo_gsm_tester/resource.py
index ad8f4b2..bff8282 100644
--- a/src/osmo_gsm_tester/resource.py
+++ b/src/osmo_gsm_tester/resource.py
@@ -109,7 +109,7 @@
         'modem[].features[]': schema.MODEM_FEATURE,
         'modem[].rf_dev_type': schema.STR,
         'modem[].rf_dev_args': schema.STR,
-        'modem[].num_carriers': schema.STR,
+        'modem[].num_carriers': schema.UINT,
         'modem[].additional_args': schema.STR,
         'modem[].airplane_t_on_ms': schema.INT,
         'modem[].airplane_t_off_ms': schema.INT,