diff --git a/lib/src/upper/rlc_am.cc b/lib/src/upper/rlc_am.cc
index b62a7e88e..96b231a09 100644
--- a/lib/src/upper/rlc_am.cc
+++ b/lib/src/upper/rlc_am.cc
@@ -613,7 +613,7 @@ int  rlc_am::build_data_pdu(uint8_t *payload, uint32_t nof_bytes)
   uint32_t pdu_space = nof_bytes;
   uint8_t *pdu_ptr   = pdu->msg;
 
-  if(pdu_space <= head_len)
+  if(pdu_space <= head_len + 1)
   {
     log->warning("%s Cannot build a PDU - %d bytes available, %d bytes required for header\n",
                  rrc->get_rb_name(lcid).c_str(), nof_bytes, head_len);
@@ -652,7 +652,7 @@ int  rlc_am::build_data_pdu(uint8_t *payload, uint32_t nof_bytes)
   }
 
   // Pull SDUs from queue
-  while(pdu_space > head_len && tx_sdu_queue.size() > 0)
+  while(pdu_space > head_len + 1 && tx_sdu_queue.size() > 0)
   {
     if(last_li > 0)
       header.li[header.N_li++] = last_li;
diff --git a/lib/test/upper/rlc_am_test.cc b/lib/test/upper/rlc_am_test.cc
index 7a37d0d5d..9ada2ba42 100644
--- a/lib/test/upper/rlc_am_test.cc
+++ b/lib/test/upper/rlc_am_test.cc
@@ -123,7 +123,7 @@ void basic_test()
   byte_buffer_t pdu_bufs[NBUFS];
   for(int i=0;i<NBUFS;i++)
   {
-    len = rlc1.read_pdu(pdu_bufs[i].msg, 3); // 3 bytes for header + payload
+    len = rlc1.read_pdu(pdu_bufs[i].msg, 4); // 3 bytes for header + payload
     pdu_bufs[i].N_bytes = len;
   }
 
@@ -351,7 +351,7 @@ void retx_test()
   byte_buffer_t pdu_bufs[NBUFS];
   for(int i=0;i<NBUFS;i++)
   {
-    len = rlc1.read_pdu(pdu_bufs[i].msg, 3); // 2 byte header + 1 byte payload
+    len = rlc1.read_pdu(pdu_bufs[i].msg, 4); // 2 byte header + 1 byte payload
     pdu_bufs[i].N_bytes = len;
   }