diff --git a/trick_source/sim_services/VariableServer/VariableServerThread_commands.cpp b/trick_source/sim_services/VariableServer/VariableServerThread_commands.cpp
index cb182d86..17ca85ab 100644
--- a/trick_source/sim_services/VariableServer/VariableServerThread_commands.cpp
+++ b/trick_source/sim_services/VariableServer/VariableServerThread_commands.cpp
@@ -124,51 +124,53 @@ int Trick::VariableServerThread::var_units(std::string var_name, std::string uni
             oss << "Variable Server: " << message << std::endl;
             message_publish(type, oss.str().c_str());
         };
+        /* if unitless ('--') then do not convert to udunits*/
+        if(units_name.compare("--")){
+            std::string new_units = map_trick_units_to_udunits(units_name) ;
+            if ( units_name.compare(new_units) ) {
+                std::ostringstream oss;
+                oss << "[" << var_name << "] old-style units converted from ["
+                    << units_name << "] to [" << new_units << "]";
+                publish(MSG_WARNING, oss.str());
+            }
 
-        std::string new_units = map_trick_units_to_udunits(units_name) ;
-        if ( units_name.compare(new_units) ) {
-            std::ostringstream oss;
-            oss << "[" << var_name << "] old-style units converted from ["
-                << units_name << "] to [" << new_units << "]";
-            publish(MSG_WARNING, oss.str());
-        }
+            auto publishError = [&](const std::string& units) {
+                std::ostringstream oss;
+                oss << "units error for [" << var_name << "] [" << units << "]";
+                publish(MSG_ERROR, oss.str());
+            };
 
-        auto publishError = [&](const std::string& units) {
-            std::ostringstream oss;
-            oss << "units error for [" << var_name << "] [" << units << "]";
-            publish(MSG_ERROR, oss.str());
-        };
+            ut_unit * from = ut_parse(Trick::UdUnits::get_u_system(), variable->ref->attr->units, UT_ASCII) ;
+            if ( !from ) {
+                publishError(variable->ref->attr->units);
+                ut_free(from) ;
+                return -1 ;
+            }
 
-        ut_unit * from = ut_parse(Trick::UdUnits::get_u_system(), variable->ref->attr->units, UT_ASCII) ;
-        if ( !from ) {
-            publishError(variable->ref->attr->units);
-            ut_free(from) ;
-            return -1 ;
-        }
+            ut_unit * to = ut_parse(Trick::UdUnits::get_u_system(), new_units.c_str(), UT_ASCII) ;
+            if ( !to ) {
+                publishError(new_units);
+                ut_free(from) ;
+                ut_free(to) ;
+                return -1 ;
+            }
 
-        ut_unit * to = ut_parse(Trick::UdUnits::get_u_system(), new_units.c_str(), UT_ASCII) ;
-        if ( !to ) {
-            publishError(new_units);
+            cv_converter * conversion_factor = ut_get_converter(from, to) ;
             ut_free(from) ;
             ut_free(to) ;
-            return -1 ;
-        }
+            if ( !conversion_factor ) {
+                std::ostringstream oss;
+                oss << "[" << var_name << "] cannot convert units from [" << variable->ref->attr->units
+                    << "] to [" << new_units << "]";
+                publish(MSG_ERROR, oss.str());
+                return -1 ;
+            }
 
-        cv_converter * conversion_factor = ut_get_converter(from, to) ;
-        ut_free(from) ;
-        ut_free(to) ;
-        if ( !conversion_factor ) {
-            std::ostringstream oss;
-            oss << "[" << var_name << "] cannot convert units from [" << variable->ref->attr->units
-                << "] to [" << new_units << "]";
-            publish(MSG_ERROR, oss.str());
-            return -1 ;
+            cv_free(variable->conversion_factor);
+            variable->conversion_factor = conversion_factor ;
+            free(variable->ref->units);
+            variable->ref->units = strdup(new_units.c_str());
         }
-
-        cv_free(variable->conversion_factor);
-        variable->conversion_factor = conversion_factor ;
-        free(variable->ref->units);
-        variable->ref->units = strdup(new_units.c_str());
     }
     return(0) ;
 }