diff --git a/openair2/LAYER2/NR_MAC_UE/nr_ue_scheduler.c b/openair2/LAYER2/NR_MAC_UE/nr_ue_scheduler.c
index 8e4fbf7154..29434b2473 100644
--- a/openair2/LAYER2/NR_MAC_UE/nr_ue_scheduler.c
+++ b/openair2/LAYER2/NR_MAC_UE/nr_ue_scheduler.c
@@ -3588,7 +3588,20 @@ static uint8_t nr_ue_get_sdu(NR_UE_MAC_INST_t *mac,
     LOG_D(NR_MAC, "Filling remainder %d bytes to the UL PDU \n", remain);
     *(NR_MAC_SUBHEADER_FIXED *)mac_ce_info.cur_ptr = (NR_MAC_SUBHEADER_FIXED){.R = 0, .LCID = UL_SCH_LCID_PADDING};
     mac_ce_info.cur_ptr++;
-    memset(mac_ce_info.cur_ptr, 0, mac_ce_info.pdu_end - mac_ce_info.cur_ptr);
+    if (get_softmodem_params()->phy_test || get_softmodem_params()->do_ra) {
+      uint8_t *buf = mac_ce_info.cur_ptr;
+      uint8_t *end = mac_ce_info.pdu_end;
+      for (; buf < end && ((intptr_t)buf) % 4; buf++)
+        *buf = lrand48() & 0xff;
+      for (; buf < end - 3; buf += 4) {
+        uint32_t *buf32 = (uint32_t *)buf;
+        *buf32 = lrand48();
+      }
+      for (; buf < end; buf++)
+        *buf = lrand48() & 0xff;
+    } else {
+      memset(mac_ce_info.cur_ptr, 0, mac_ce_info.pdu_end - mac_ce_info.cur_ptr);
+    }
   }
 #ifdef ENABLE_MAC_PAYLOAD_DEBUG
   LOG_I(NR_MAC, "MAC PDU %d bytes \n", mac_ce_p->cur_ptr - ulsch_buffer);