diff --git a/libraries/AP_Networking/lwip_hal/arch/evtimer.c b/libraries/AP_Networking/lwip_hal/arch/evtimer.c
new file mode 100644
index 0000000000..53da0413f8
--- /dev/null
+++ b/libraries/AP_Networking/lwip_hal/arch/evtimer.c
@@ -0,0 +1,10 @@
+/*
+  wrapper around evtimer.c so we only build when events are
+  enabled. This prevents a complex check in the ChibiOS mk layer
+ */
+#include <hal.h>
+
+#if CH_CFG_USE_EVENTS
+#include "../../modules/ChibiOS/os/various/evtimer.c"
+#endif
+
diff --git a/libraries/AP_Networking/wscript b/libraries/AP_Networking/wscript
index 4094b6aeaf..97554622a7 100644
--- a/libraries/AP_Networking/wscript
+++ b/libraries/AP_Networking/wscript
@@ -25,6 +25,10 @@ def configure(cfg):
     ]
 
     extra_src.extend(['libraries/AP_Networking/lwip_hal/arch/*cpp'])
+
+    if cfg.env.BOARD_CLASS == 'ChibiOS':
+        extra_src.extend(['libraries/AP_Networking/lwip_hal/arch/evtimer.c'])
+
     extra_src_inc.extend(['libraries/AP_Networking/config',
                           'libraries/AP_Networking/lwip_hal/include'])