diff --git a/firmware/fsm.c b/firmware/fsm.c
index 837dc5f..fa9a5d9 100644
--- a/firmware/fsm.c
+++ b/firmware/fsm.c
@@ -51,7 +51,9 @@
 
 static uint8_t msg_resp[MSG_OUT_SIZE];
 
-#define RESP_INIT(TYPE) TYPE *resp = (TYPE *)msg_resp; memset(resp, 0, sizeof(TYPE));
+#define RESP_INIT(TYPE) TYPE *resp = (TYPE *)msg_resp; \
+			_Static_assert(sizeof(msg_resp) >= sizeof(TYPE), #TYPE " is too large"); \
+			memset(resp, 0, sizeof(TYPE));
 
 void fsm_sendSuccess(const char *text)
 {