diff --git a/selfdrive/locationd/ublox_msg.cc b/selfdrive/locationd/ublox_msg.cc
index 8fa721a091..b746989466 100644
--- a/selfdrive/locationd/ublox_msg.cc
+++ b/selfdrive/locationd/ublox_msg.cc
@@ -359,6 +359,9 @@ kj::Array<capnp::word> UbloxMsgParser::parse_glonass_ephemeris(ubx_t::rxm_sfrbx_
     eph.setAge(data->e_n());
     eph.setP4(data->p4());
     eph.setSvURA(glonass_URA_lookup.at(data->f_t()));
+    if (msg->sv_id() != data->n()) {
+      LOGE("SV_ID != SLOT_NUMBER: %d %d", msg->sv_id(), data->n())
+    }
     eph.setSvType(data->m());
   }