diff --git a/impl/src/layer2/layer2_rx.c b/impl/src/layer2/layer2_rx.c
index 2b67379..86a5798 100644
--- a/impl/src/layer2/layer2_rx.c
+++ b/impl/src/layer2/layer2_rx.c
@@ -64,6 +64,10 @@ result_t layer2_rx_handle_packet(layer2_rx_t *ctx, const uint8_t *buf, size_t bu
 
 		case L2_MSG_TYPE_DATA:
 			break;
+
+		default:
+			LOG(LVL_ERR, "Invalid message type %d.", header.msg_type);
+			return ERR_INVALID_STATE;
 	}
 
 	if(ctx->next_expected_seq != header.tx_seq_nr) {