diff --git a/lib/src/upper/rlc_um.cc b/lib/src/upper/rlc_um.cc
index 045fb0b7e..d95e186e7 100644
--- a/lib/src/upper/rlc_um.cc
+++ b/lib/src/upper/rlc_um.cc
@@ -277,7 +277,7 @@ int  rlc_um::build_data_pdu(uint8_t *payload, uint32_t nof_bytes)
   int head_len  = rlc_um_packed_length(&header);
   int pdu_space = nof_bytes;
 
-  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);
diff --git a/lib/test/upper/rlc_um_test.cc b/lib/test/upper/rlc_um_test.cc
index 0894a2a8b..8abcfae3c 100644
--- a/lib/test/upper/rlc_um_test.cc
+++ b/lib/test/upper/rlc_um_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;
   }
 
@@ -191,7 +191,7 @@ void loss_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;
   }