diff --git a/sim_tmxr.c b/sim_tmxr.c
index ff2c46d9..b1fb7089 100644
--- a/sim_tmxr.c
+++ b/sim_tmxr.c
@@ -2561,7 +2561,7 @@ if ((mp->lines > 1) ||
     ((mp->master == 0) &&
      (mp->ldsc[0].connecting == 0) &&
      (mp->ldsc[0].serport == 0)))
-    uptr->flags = uptr->dynflags | UNIT_ATTMULT;        /* allow multiple attach commands */
+    uptr->dynflags = uptr->dynflags | UNIT_ATTMULT;     /* allow multiple attach commands */
 
 #if defined(SIM_ASYNCH_IO) && defined(SIM_ASYNCH_MUX)
 if (!async || (uptr->flags & TMUF_NOASYNCH))            /* if asynch disabled */