p = (StgClosure *)deRefStablePtr(s);
tso = createStrictIOThread(cap, RtsFlags.GcFlags.initialStkSize, p);
+ // async exceptions are always blocked by default in the created
+ // thread. See #1048.
+ tso->flags |= TSO_BLOCKEX | TSO_INTERRUPTIBLE;
cap = scheduleWaitThread(tso,&r,cap);
stat = rts_getSchedStatus(cap);