diff --git a/src/sys_fst.c b/src/sys_fst.c
index 5360828..2238143 100644
--- a/src/sys_fst.c
+++ b/src/sys_fst.c
@@ -945,6 +945,8 @@ void sys_fst_register(void)
       s_vpi_systf_data tf_data;
       vpiHandle res;
 
+#ifdef EXTENDED_ARGS
+
 	/* Scan the extended arguments, looking for fst optimization flags. */
       vpi_get_vlog_info(&vlog_info);
 
@@ -963,6 +965,8 @@ void sys_fst_register(void)
 	    }
       }
 
+#endif
+
       /* All the compiletf routines are located in vcd_priv.c. */
 
       tf_data.type      = vpiSysTask;