diff --git a/tests/net/nanocoap_cli/nanocli_client.c b/tests/net/nanocoap_cli/nanocli_client.c
index 3266c69055d0..2f8351a14ed2 100644
--- a/tests/net/nanocoap_cli/nanocli_client.c
+++ b/tests/net/nanocoap_cli/nanocli_client.c
@@ -327,7 +327,7 @@ int nanotest_client_get_non_cmd(int argc, char **argv)
 {
     int res;
 
-    uint8_t response[CONFIG_NANOCOAP_BLOCKSIZE_DEFAULT];
+    uint8_t response[coap_szx2size(CONFIG_NANOCOAP_BLOCKSIZE_DEFAULT)];
 
     if (argc < 2) {
         printf("usage: %s <url>\n", argv[0]);