diff --git a/srsenb/hdr/phy/phch_common.h b/srsenb/hdr/phy/phch_common.h
index b94042182..03cff5eaf 100644
--- a/srsenb/hdr/phy/phch_common.h
+++ b/srsenb/hdr/phy/phch_common.h
@@ -166,7 +166,8 @@ private:
   uint8_t mch_sf_idx_lut[10];
   bool is_mch_subframe(subframe_cfg_t *cfg, uint32_t phy_tti);
   bool is_mcch_subframe(subframe_cfg_t *cfg, uint32_t phy_tti);
-  
+
+  void add_rnti(uint16_t rnti);
   
 };
 
diff --git a/srsenb/src/phy/phch_common.cc b/srsenb/src/phy/phch_common.cc
index 9b3ea75e0..536b0a358 100644
--- a/srsenb/src/phy/phch_common.cc
+++ b/srsenb/src/phy/phch_common.cc
@@ -108,12 +108,18 @@ void phch_common::ue_db_clear(uint32_t sf_idx)
 void phch_common::ue_db_add_rnti(uint16_t rnti)
 {
   pthread_mutex_lock(&user_mutex);
+  add_rnti(rnti);
+  pthread_mutex_unlock(&user_mutex);
+}
+
+// Private function not mutexed
+void phch_common::add_rnti(uint16_t rnti)
+{
   for (int sf_idx=0;sf_idx<TTIMOD_SZ;sf_idx++) {
     for (uint32_t tb_idx = 0; tb_idx < SRSLTE_MAX_TB; tb_idx++) {
       common_ue_db[rnti].pending_ack.is_pending[sf_idx][tb_idx] = false;
     }
   }
-  pthread_mutex_unlock(&user_mutex);
 }
 
 void phch_common::ue_db_rem_rnti(uint16_t rnti)
@@ -172,7 +178,7 @@ void phch_common::ue_db_set_last_ul_mod(uint16_t rnti, uint32_t tti, srslte_mod_
 {
   pthread_mutex_lock(&user_mutex);
   if (!common_ue_db.count(rnti)) {
-    ue_db_add_rnti(rnti);
+    add_rnti(rnti);
   }
   common_ue_db[rnti].last_ul_mod[TTI_RX(tti)%(2*HARQ_DELAY_MS)] = mcs;
   pthread_mutex_unlock(&user_mutex);
@@ -185,15 +191,15 @@ srslte_mod_t phch_common::ue_db_get_last_ul_mod(uint16_t rnti, uint32_t tti)
   if (common_ue_db.count(rnti)) {
     ret = common_ue_db[rnti].last_ul_mod[TTI_RX(tti)%(2*HARQ_DELAY_MS)];
   }
-  return ret;
   pthread_mutex_unlock(&user_mutex);
+  return ret;
 }
 
 void phch_common::ue_db_set_last_ul_tbs(uint16_t rnti, uint32_t tti, int tbs)
 {
   pthread_mutex_lock(&user_mutex);
   if (!common_ue_db.count(rnti)) {
-    ue_db_add_rnti(rnti);
+    add_rnti(rnti);
   }
   common_ue_db[rnti].last_ul_tbs[TTI_RX(tti)%(2*HARQ_DELAY_MS)] = tbs;
   pthread_mutex_unlock(&user_mutex);