diff --git a/gprs_bssgp_pcu.h b/gprs_bssgp_pcu.h
index 61759176..bc32173a 100644
--- a/gprs_bssgp_pcu.h
+++ b/gprs_bssgp_pcu.h
@@ -46,7 +46,7 @@ struct bssgp_bvc_ctx *btsctx_alloc(uint16_t bvci, uint16_t nsei);
 #define NS_HDR_LEN 4
 #define MAX_LEN_PDU 60
 #define IE_PDU 14
-#define BLOCK_DATA_LEN 19
+#define BLOCK_DATA_LEN 20
 #define BLOCK_LEN 23
 
 #define CELL_ID 3
diff --git a/gprs_rlcmac.cpp b/gprs_rlcmac.cpp
index 80814c02..57484112 100644
--- a/gprs_rlcmac.cpp
+++ b/gprs_rlcmac.cpp
@@ -603,7 +603,7 @@ void gprs_rlcmac_tx_dl_data_block(uint32_t tlli, uint8_t tfi, uint8_t *pdu, int
 	data_block->TFI = tfi;
 	data_block->FBI = fbi;
 	data_block->BSN = bsn;
-	if ((end_index - start_index) < 20) {
+	if ((end_index - start_index) < 19) {
 		data_block->E_1 = 0;
 		data_block->LENGTH_INDICATOR[0] = end_index-start_index;
 		data_block->M[0] = 0;