diff --git a/srsue/src/stack/mac_nr/mux_nr.cc b/srsue/src/stack/mac_nr/mux_nr.cc
index 001dea03f..3fd79f01f 100644
--- a/srsue/src/stack/mac_nr/mux_nr.cc
+++ b/srsue/src/stack/mac_nr/mux_nr.cc
@@ -94,10 +94,10 @@ srsran::unique_byte_buffer_t mux_nr::get_pdu(uint32_t max_pdu_len)
         uint8_t* rd = rlc_buff->msg;
 
         // Determine space for RLC
-        remaining_len -= remaining_len >= srsran::mac_sch_subpdu_nr::MAC_SUBHEADER_LEN_THRESHOLD ? 3 : 2;
+        int32_t subpdu_header_len = (remaining_len >= srsran::mac_sch_subpdu_nr::MAC_SUBHEADER_LEN_THRESHOLD ? 3 : 2);
 
-        // Read PDU from RLC
-        int pdu_len = rlc->read_pdu(lc.lcid, rd, remaining_len);
+        // Read PDU from RLC (account for subPDU header)
+        int pdu_len = rlc->read_pdu(lc.lcid, rd, remaining_len - subpdu_header_len);
 
         if (pdu_len > remaining_len) {
           logger.error("Can't add SDU of %d B. Available space %d B", pdu_len, remaining_len);
@@ -114,10 +114,11 @@ srsran::unique_byte_buffer_t mux_nr::get_pdu(uint32_t max_pdu_len)
               break;
             }
           } else {
+            // couldn't read PDU from RLC
             break;
           }
 
-          remaining_len -= pdu_len;
+          remaining_len -= (pdu_len + subpdu_header_len);
           logger.debug("%d B remaining PDU", remaining_len);
         }
       }