diff --git a/srsue/src/stack/mac_nr/mac_nr.cc b/srsue/src/stack/mac_nr/mac_nr.cc
index bfbd15824..53d2253fa 100644
--- a/srsue/src/stack/mac_nr/mac_nr.cc
+++ b/srsue/src/stack/mac_nr/mac_nr.cc
@@ -128,7 +128,8 @@ void mac_nr::update_buffer_states()
     mac_buffer_states.lcid_buffer_size[channel.lcid] += buffer_len;
     mac_buffer_states.lcg_buffer_size[channel.lcg] += buffer_len;
   }
-  logger.info("%s", mac_buffer_states.to_string());
+  logger.debug("%s", mac_buffer_states.to_string());
+
   // Count TTI for metrics
   for (uint32_t i = 0; i < SRSRAN_MAX_CARRIERS; ++i) {
     metrics[i].nof_tti++;
@@ -286,11 +287,15 @@ void mac_nr::new_grant_ul(const uint32_t cc_idx, const mac_nr_grant_ul_t& grant,
   ul_harq_buffer = mux.get_pdu(grant.tbs);
 
   // fill TB action (goes into UL harq eventually)
-  action->tb.payload    = ul_harq_buffer.get(); // pass handle to PDU to PHY
-  action->tb.enabled    = true;
-  action->tb.rv         = 0;
-  action->tb.softbuffer = &softbuffer_tx;
-  srsran_softbuffer_tx_reset(&softbuffer_tx);
+  if (ul_harq_buffer != nullptr) {
+    action->tb.payload    = ul_harq_buffer.get(); // pass handle to PDU to PHY
+    action->tb.enabled    = true;
+    action->tb.rv         = 0;
+    action->tb.softbuffer = &softbuffer_tx;
+    srsran_softbuffer_tx_reset(&softbuffer_tx);
+  } else {
+    action->tb.enabled = false;
+  }
 
   // store PCAP
   if (pcap) {
diff --git a/srsue/src/stack/mac_nr/mux_nr.cc b/srsue/src/stack/mac_nr/mux_nr.cc
index a33213516..f949d960b 100644
--- a/srsue/src/stack/mac_nr/mux_nr.cc
+++ b/srsue/src/stack/mac_nr/mux_nr.cc
@@ -49,6 +49,12 @@ srsran::unique_byte_buffer_t mux_nr::get_pdu(uint32_t max_pdu_len)
     return nullptr;
   }
 
+  // verify buffer is large enough for UL grant
+  if (phy_tx_pdu->get_tailroom() < max_pdu_len) {
+    logger.error("Can't provide MAC PDU. Grant too big (%d < %d).", phy_tx_pdu->get_tailroom(), max_pdu_len);
+    return nullptr;
+  }
+
   logger.debug("Building new MAC PDU (%d B)", max_pdu_len);
   tx_pdu.init_tx(phy_tx_pdu.get(), max_pdu_len, true);
 
diff --git a/srsue/src/stack/mac_nr/proc_bsr_nr.cc b/srsue/src/stack/mac_nr/proc_bsr_nr.cc
index 5ea11ecc8..afb6aca56 100644
--- a/srsue/src/stack/mac_nr/proc_bsr_nr.cc
+++ b/srsue/src/stack/mac_nr/proc_bsr_nr.cc
@@ -199,8 +199,10 @@ bool proc_bsr_nr::check_new_data(const mac_buffer_states_t& new_buffer_state)
 srsran::mac_sch_subpdu_nr::lcg_bsr_t proc_bsr_nr::generate_sbsr()
 {
   srsran::mac_sch_subpdu_nr::lcg_bsr_t sbsr = {};
-  sbsr.lcg_id                               = buffer_state.last_non_zero_lcg;
-  sbsr.buffer_size   = buff_size_bytes_to_field(buffer_state.lcg_buffer_size.at(sbsr.lcg_id), SHORT_BSR);
+  if (buffer_state.nof_lcgs_with_data > 0) {
+    sbsr.lcg_id      = buffer_state.last_non_zero_lcg;
+    sbsr.buffer_size = buff_size_bytes_to_field(buffer_state.lcg_buffer_size.at(sbsr.lcg_id), SHORT_BSR);
+  }
   triggered_bsr_type = NONE;
   return sbsr;
 }