diff --git a/lib/include/srslte/upper/rlc_common.h b/lib/include/srslte/upper/rlc_common.h
index 71fe934df..3b1cec6a2 100644
--- a/lib/include/srslte/upper/rlc_common.h
+++ b/lib/include/srslte/upper/rlc_common.h
@@ -37,7 +37,7 @@ namespace srslte {
  ***************************************************************************/
 
 #define RLC_AM_WINDOW_SIZE  512
-
+#define RLC_MAX_SDU_SIZE ((1<<11)-1) // Length of LI field is 11bits
 
 
 typedef enum{
diff --git a/lib/include/srslte/upper/rlc_um.h b/lib/include/srslte/upper/rlc_um.h
index 92a7822d5..b0fb2c13d 100644
--- a/lib/include/srslte/upper/rlc_um.h
+++ b/lib/include/srslte/upper/rlc_um.h
@@ -39,8 +39,6 @@
 
 namespace srslte {
 
-#define RLC_UM_MAX_SDU_SIZE (2048-1) // Length of LI field is 11bits
-
 struct rlc_umd_pdu_t{
   rlc_umd_pdu_header_t  header;
   byte_buffer_t        *buf;
diff --git a/lib/src/upper/rlc.cc b/lib/src/upper/rlc.cc
index 5cf561415..886de474a 100644
--- a/lib/src/upper/rlc.cc
+++ b/lib/src/upper/rlc.cc
@@ -210,6 +210,13 @@ void rlc::empty_queue()
 
 void rlc::write_sdu(uint32_t lcid, byte_buffer_t *sdu, bool blocking)
 {
+  // FIXME: rework build PDU logic to allow large SDUs (without concatenation)
+  if (sdu->N_bytes > RLC_MAX_SDU_SIZE) {
+    rlc_log->warning("Dropping too long SDU of size %d B (Max. size %d B).\n", sdu->N_bytes, RLC_MAX_SDU_SIZE);
+    pool->deallocate(sdu);
+    return;
+  }
+
   pthread_rwlock_rdlock(&rwlock);
   if (valid_lcid(lcid)) {
     rlc_array.at(lcid)->write_sdu(sdu, blocking);
diff --git a/lib/src/upper/rlc_am.cc b/lib/src/upper/rlc_am.cc
index 7c2e18b0f..bd0acbeff 100644
--- a/lib/src/upper/rlc_am.cc
+++ b/lib/src/upper/rlc_am.cc
@@ -920,7 +920,7 @@ int rlc_am::rlc_am_tx::build_data_pdu(uint8_t *payload, uint32_t nof_bytes)
   }
 
   // Pull SDUs from queue
-  while (pdu_space > head_len + 1 && tx_sdu_queue.size() > 0) {
+  while (pdu_space > head_len + 1 && tx_sdu_queue.size() > 0 && header.N_li < RLC_AM_WINDOW_SIZE) {
     if (last_li > 0) {
       header.li[header.N_li] = last_li;
       header.N_li++;
diff --git a/lib/src/upper/rlc_um.cc b/lib/src/upper/rlc_um.cc
index 7145a8b66..4fee0e7b6 100644
--- a/lib/src/upper/rlc_um.cc
+++ b/lib/src/upper/rlc_um.cc
@@ -151,11 +151,6 @@ uint32_t rlc_um::get_bearer()
  ***************************************************************************/
 void rlc_um::write_sdu(byte_buffer_t *sdu, bool blocking)
 {
-  if (sdu->N_bytes > RLC_UM_MAX_SDU_SIZE) {
-    log->warning("Dropping too long SDU of size %d B (Max. size %d B).", sdu->N_bytes, RLC_UM_MAX_SDU_SIZE);
-    pool->deallocate(sdu);
-  }
-
   if (blocking) {
     tx.write_sdu(sdu);
   } else {