diff --git a/srsue/hdr/stack/ue_stack_base.h b/srsue/hdr/stack/ue_stack_base.h
index 5a16b8637..1de62f8a8 100644
--- a/srsue/hdr/stack/ue_stack_base.h
+++ b/srsue/hdr/stack/ue_stack_base.h
@@ -68,6 +68,7 @@ typedef struct {
   std::string      ue_category_str;
   nas_args_t       nas;
   gw_args_t        gw;
+  uint32_t         sync_queue_size; // Max allowed difference between PHY and Stack clocks (in TTI)
   bool             have_tti_time_stats;
 } stack_args_t;
 
diff --git a/srsue/src/main.cc b/srsue/src/main.cc
index 263283757..6d3d3732b 100644
--- a/srsue/src/main.cc
+++ b/srsue/src/main.cc
@@ -558,6 +558,14 @@ static int parse_args(all_args_t* args, int argc, char* argv[])
     }
   }
 
+  // Set sync queue capacity to 1 for ZMQ
+  if (args->rf.device_name == "zmq") {
+    args->stack.sync_queue_size = 1;
+  } else {
+    // use default size
+    args->stack.sync_queue_size = MULTIQUEUE_DEFAULT_CAPACITY;
+  }
+
   return SRSLTE_SUCCESS;
 }
 
diff --git a/srsue/src/stack/ue_stack_lte.cc b/srsue/src/stack/ue_stack_lte.cc
index 3ca6ad318..b18ffce83 100644
--- a/srsue/src/stack/ue_stack_lte.cc
+++ b/srsue/src/stack/ue_stack_lte.cc
@@ -49,10 +49,10 @@ ue_stack_lte::ue_stack_lte() :
   tti_tprof("tti_tprof", "STCK", TTI_STAT_PERIOD)
 {
   ue_queue_id         = pending_tasks.add_queue();
-  sync_queue_id       = pending_tasks.add_queue();
   gw_queue_id         = pending_tasks.add_queue();
   stack_queue_id      = pending_tasks.add_queue();
   background_queue_id = pending_tasks.add_queue();
+  // sync_queue is added in init()
 
   background_tasks.start();
 }
@@ -125,6 +125,9 @@ int ue_stack_lte::init(const stack_args_t& args_, srslte::logger* logger_)
     return SRSLTE_ERROR;
   }
 
+  // add sync queue
+  sync_queue_id = pending_tasks.add_queue(args.sync_queue_size);
+
   mac.init(phy, &rlc, &rrc, this);
   rlc.init(&pdcp, &rrc, &timers, 0 /* RB_ID_SRB0 */);
   pdcp.init(&rlc, &rrc, gw);
diff --git a/srsue/test/ttcn3/src/ttcn3_dut.cc b/srsue/test/ttcn3/src/ttcn3_dut.cc
index a9c2a6e3d..912bdbaa6 100644
--- a/srsue/test/ttcn3/src/ttcn3_dut.cc
+++ b/srsue/test/ttcn3/src/ttcn3_dut.cc
@@ -106,6 +106,8 @@ all_args_t parse_args(ttcn3_dut_args_t* args, int argc, char* argv[])
   all_args.stack.log.gw_hex_limit   = args->log_hex_level;
   all_args.stack.log.usim_hex_limit = args->log_hex_level;
 
+  all_args.stack.sync_queue_size = 1;
+
   return all_args;
 }