diff --git a/src/apps/lwiperf/lwiperf.c b/src/apps/lwiperf/lwiperf.c
index f6ab39c7..ec30fb4d 100644
--- a/src/apps/lwiperf/lwiperf.c
+++ b/src/apps/lwiperf/lwiperf.c
@@ -112,7 +112,7 @@ typedef struct _lwiperf_state_tcp {
 /** List of active iperf sessions */
 static lwiperf_state_base_t* lwiperf_all_connections;
 /** A const buffer to send from: we want to measure sending, not copying! */
-const u8_t lwiperf_txbuf_const[1600] = {
+static const u8_t lwiperf_txbuf_const[1600] = {
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