diff --git a/targets/TARGET_Maxim/TARGET_MAX32620C/serial_api.c b/targets/TARGET_Maxim/TARGET_MAX32620C/serial_api.c
index f02ae70f43..b51826815b 100644
--- a/targets/TARGET_Maxim/TARGET_MAX32620C/serial_api.c
+++ b/targets/TARGET_Maxim/TARGET_MAX32620C/serial_api.c
@@ -418,3 +418,8 @@ const PinMap *serial_rts_pinmap()
 {
     return PinMap_UART_RTS;
 }
+
+void serial_free(serial_t *obj)
+{
+    // Not implemented
+}