diff --git a/src/modules/tmr.c b/src/modules/tmr.c
index a4e1bd76..e5ca8f60 100644
--- a/src/modules/tmr.c
+++ b/src/modules/tmr.c
@@ -200,8 +200,10 @@ const LUA_REG_TYPE tmr_map[] =
 #endif
 #if VTMR_NUM_TIMERS > 0  
   { LSTRKEY( "__index" ), LFUNCVAL( tmr_mt_index ) },
-  { LSTRKEY( "SYS_TIMER" ), LNUMVAL( PLATFORM_TIMER_SYS_ID ) },
 #endif  
+#if LUA_OPTIMIZE_MEMORY > 0
+  { LSTRKEY( "SYS_TIMER" ), LNUMVAL( PLATFORM_TIMER_SYS_ID ) },
+#endif
 #if LUA_OPTIMIZE_MEMORY > 0 && defined( BUILD_LUA_INT_HANDLERS )
   { LSTRKEY( "INT_ONESHOT" ), LNUMVAL( PLATFORM_TIMER_INT_ONESHOT ) },
   { LSTRKEY( "INT_CYCLIC" ), LNUMVAL( PLATFORM_TIMER_INT_CYCLIC ) },