diff --git a/sys/include/net/gnrc/tcp/config.h b/sys/include/net/gnrc/tcp/config.h
index 5a92a6e041..6f89b3f2e2 100644
--- a/sys/include/net/gnrc/tcp/config.h
+++ b/sys/include/net/gnrc/tcp/config.h
@@ -128,8 +128,8 @@ extern "C" {
 /**
  * @brief Assumes clock granularity for TCP of 10 ms (see RFC 6298)
  */
-#ifndef GNRC_TCP_RTO_GRANULARITY
-#define GNRC_TCP_RTO_GRANULARITY (10U * MS_PER_SEC)
+#ifndef CONFIG_GNRC_TCP_RTO_GRANULARITY
+#define CONFIG_GNRC_TCP_RTO_GRANULARITY (10U * MS_PER_SEC)
 #endif
 
 /**
diff --git a/sys/net/gnrc/transport_layer/tcp/gnrc_tcp_pkt.c b/sys/net/gnrc/transport_layer/tcp/gnrc_tcp_pkt.c
index cbf345168e..827a75842b 100644
--- a/sys/net/gnrc/transport_layer/tcp/gnrc_tcp_pkt.c
+++ b/sys/net/gnrc/transport_layer/tcp/gnrc_tcp_pkt.c
@@ -388,7 +388,7 @@ int _pkt_setup_retransmit(gnrc_tcp_tcb_t *tcb, gnrc_pktsnip_t *pkt, const bool r
             tcb->rto = CONFIG_GNRC_TCP_RTO_LOWER_BOUND;
         }
         else {
-            tcb->rto = tcb->srtt + _max(GNRC_TCP_RTO_GRANULARITY,  GNRC_TCP_RTO_K * tcb->rtt_var);
+            tcb->rto = tcb->srtt + _max(CONFIG_GNRC_TCP_RTO_GRANULARITY, GNRC_TCP_RTO_K * tcb->rtt_var);
         }
     }
     else {