diff --git a/mps/src/poolamc.c b/mps/src/poolamc.c
index 8557299dfb7..b8e4fa01eb3 100644
--- a/mps/src/poolamc.c
+++ b/mps/src/poolamc.c
@@ -1,6 +1,6 @@
 /* impl.c.poolamc: AUTOMATIC MOSTLY-COPYING MEMORY POOL CLASS
  *
- * $HopeName: MMsrc!poolamc.c(trunk.41) $
+ * $HopeName: MMsrc!poolamc.c(trunk.42) $
  * Copyright (C) 2000 Harlequin Limited.  All rights reserved.
  *
  * .sources: design.mps.poolamc.
@@ -9,7 +9,7 @@
 #include "mpscamc.h"
 #include "mpm.h"
 
-SRCID(poolamc, "$HopeName: MMsrc!poolamc.c(trunk.41) $");
+SRCID(poolamc, "$HopeName: MMsrc!poolamc.c(trunk.42) $");
 
 
 /* PType enumeration -- distinguishes AMCGen and AMCNailBoard */
@@ -1144,6 +1144,10 @@ static Res AMCWhiten(Pool pool, Trace trace, Seg seg)
     }
   }
 
+  /* .act.survivors: Whiten inits survivors; Reclaim will decrement it. */
+  /* .stop.restart: Stops AMCBenefit from trying to restart the trace. */
+  gen->survivors = gen->size;
+
   return ResOK;
 }
 
@@ -1283,24 +1287,18 @@ static Res AMCAct(Pool pool, Action action)
   res = amcCondemnGens(amc, trace, topCondemnedGenSerial);
   if (res != ResOK)
     goto failCondemn;
-  /* .act.survivors: Act inits survivors; Reclaim will decrement it. */
-  /* .stop.restart: Stops AMCBenefit from trying to restart the trace. */
-  currGenSerial = 0;
-  do {
-    gen = amc->gen[currGenSerial];
-    AVERT(AMCGen, gen);
-    gen->survivors = gen->size;
-    if (currGenSerial == topCondemnedGenSerial) break;
-    currGenSerial = AMCGenNext(amc, currGenSerial);
-  } while (TRUE);
 
   if (topCondemnedGenSerial != TraceTopGen) {
     TraceStart(trace, TraceEphemeralMortality,
                (TraceGen0IncrementalityMultiple * TraceGen0Size * 1024uL));
   } else {
-    TraceStart(trace, TraceTopGenMortality,
-               amcArenaAvail(arena)
-               - trace->condemned * (1 - TraceTopGenMortality));
+    double finishingTime = amcArenaAvail(arena)
+                           - trace->condemned * (1.0 - TraceTopGenMortality);
+
+    if (finishingTime < 0)
+      /* Run out of time, should really try a smaller collection. @@@@ */
+      finishingTime = 0.0;
+    TraceStart(trace, TraceTopGenMortality, finishingTime);
   }
 
   return ResOK;