diff --git a/impl/src/layer2/connection.c b/impl/src/layer2/connection.c
index 87e00ab..ea25c51 100644
--- a/impl/src/layer2/connection.c
+++ b/impl/src/layer2/connection.c
@@ -29,6 +29,10 @@ result_t connection_init(connection_ctx_t *ctx, const ham64_t *my_addr, const ha
 
 void connection_destroy(connection_ctx_t *ctx)
 {
+	if(ctx->conn_state == CONN_STATE_UNINITIALIZED) {
+		return;
+	}
+
 	ctx->conn_state = CONN_STATE_UNINITIALIZED;
 	packet_queue_destroy(&ctx->packet_queue);
 }
@@ -36,6 +40,20 @@ void connection_destroy(connection_ctx_t *ctx)
 
 result_t connection_handle_packet(connection_ctx_t *ctx, const uint8_t *buf, size_t buf_len)
 {
+	// check the connection state
+	switch(ctx->conn_state) {
+		case CONN_STATE_UNINITIALIZED:
+		case CONN_STATE_INITIALIZED:
+		case CONN_STATE_CLOSED:
+			LOG(LVL_ERR, "Trying to pass packet to connection in state %u", ctx->conn_state);
+			return ERR_INVALID_STATE;
+
+		case CONN_STATE_CONNECTING:
+		case CONN_STATE_ESTABLISHED:
+			// in these states, packets can be handled
+			break;
+	}
+
 	// check the CRC
 	size_t packet_size = buf_len - crc_sizeof_key(PAYLOAD_CRC_SCHEME);
 
@@ -142,6 +160,20 @@ uint8_t connection_get_last_acked_seq(const connection_ctx_t *ctx)
 
 result_t connection_enqueue_packet(connection_ctx_t *ctx, uint8_t *buf, size_t buf_len)
 {
+	// check the connection state
+	switch(ctx->conn_state) {
+		case CONN_STATE_UNINITIALIZED:
+		case CONN_STATE_INITIALIZED:
+		case CONN_STATE_CLOSED:
+		case CONN_STATE_CONNECTING:
+			LOG(LVL_ERR, "Trying to enqueue packet in inactive state %u", ctx->conn_state);
+			return ERR_INVALID_STATE;
+
+		case CONN_STATE_ESTABLISHED:
+			// in these states, packets can be handled
+			break;
+	}
+
 	layer2_packet_header_t header;
 
 	if(packet_queue_get_free_space(&ctx->packet_queue) == 0) {
@@ -179,6 +211,20 @@ result_t connection_enqueue_packet(connection_ctx_t *ctx, uint8_t *buf, size_t b
 
 result_t connection_add_empty_packet(connection_ctx_t *ctx, bool tx_request)
 {
+	// check the connection state
+	switch(ctx->conn_state) {
+		case CONN_STATE_UNINITIALIZED:
+		case CONN_STATE_INITIALIZED:
+		case CONN_STATE_CLOSED:
+		case CONN_STATE_CONNECTING:
+			LOG(LVL_ERR, "Trying to add empty packet in inactive state %u", ctx->conn_state);
+			return ERR_INVALID_STATE;
+
+		case CONN_STATE_ESTABLISHED:
+			// in these states, packets can be handled
+			break;
+	}
+
 	layer2_packet_header_t header;
 
 	header.dst_addr.addr[0] = 0xFFFF;
@@ -200,6 +246,20 @@ result_t connection_add_empty_packet(connection_ctx_t *ctx, bool tx_request)
 
 size_t connection_encode_next_packet(connection_ctx_t *ctx, uint8_t ack_seq_nr, uint8_t *buf, size_t buf_len)
 {
+	// check the connection state
+	switch(ctx->conn_state) {
+		case CONN_STATE_UNINITIALIZED:
+		case CONN_STATE_INITIALIZED:
+		case CONN_STATE_CLOSED:
+			LOG(LVL_ERR, "Trying to encode packet in inactive state %u", ctx->conn_state);
+			return ERR_INVALID_STATE;
+
+		case CONN_STATE_CONNECTING:
+		case CONN_STATE_ESTABLISHED:
+			// in these states, packets may be present for transmission
+			break;
+	}
+
 	const packet_queue_entry_t *entry = packet_queue_get(&ctx->packet_queue, ctx->next_packet_index);
 
 	if(!entry) {
@@ -245,6 +305,8 @@ void connection_restart_tx(connection_ctx_t *ctx)
 
 void connection_tx_clean_empty_packet(connection_ctx_t *ctx)
 {
+	assert(ctx->conn_state != CONN_STATE_UNINITIALIZED);
+
 	const packet_queue_entry_t *entry = packet_queue_get(&ctx->packet_queue, 0);
 	if(entry && entry->header.msg_type == L2_MSG_TYPE_EMPTY) {
 		packet_queue_delete(&ctx->packet_queue, 1);
@@ -258,6 +320,20 @@ void connection_tx_clean_empty_packet(connection_ctx_t *ctx)
 
 void connection_handle_ack(connection_ctx_t *ctx, uint8_t acked_seq)
 {
+	// check the connection state
+	switch(ctx->conn_state) {
+		case CONN_STATE_UNINITIALIZED:
+		case CONN_STATE_INITIALIZED:
+		case CONN_STATE_CLOSED:
+		case CONN_STATE_CONNECTING:
+			LOG(LVL_ERR, "Trying to call connection_handle_ack() in inactive state %u", ctx->conn_state);
+			return;
+
+		case CONN_STATE_ESTABLISHED:
+			// in these states, packets may be present for transmission
+			break;
+	}
+
 	ctx->next_packet_index = 0;
 
 	size_t packets_to_remove = 0;
@@ -292,6 +368,8 @@ void connection_handle_ack(connection_ctx_t *ctx, uint8_t acked_seq)
 
 bool connection_can_transmit(const connection_ctx_t *ctx)
 {
+	assert(ctx->conn_state != CONN_STATE_UNINITIALIZED);
+
 	return (packet_queue_get_used_space(&ctx->packet_queue) != 0)
 		&& (packet_queue_get(&ctx->packet_queue, ctx->next_packet_index) != NULL);
 }