diff --git a/src/hci_cmds.c b/src/hci_cmds.c
index cc0e9f227..b85108c20 100644
--- a/src/hci_cmds.c
+++ b/src/hci_cmds.c
@@ -110,7 +110,7 @@ uint16_t hci_create_cmd_internal(uint8_t *hci_cmd_buffer, hci_cmd_t *cmd, va_lis
                 break;
             case 'N': { // UTF-8 string, null terminated
                 ptr = va_arg(argptr, uint8_t *);
-                uint16_t len = strlen(ptr);
+                uint16_t len = strlen((const char*) ptr);
                 if (len > 248) {
                     len = 248;
                 }