diff --git a/mps/code/global.c b/mps/code/global.c
index 55bb5013a79..a9090d00372 100644
--- a/mps/code/global.c
+++ b/mps/code/global.c
@@ -649,19 +649,51 @@ void (ArenaPoll)(Globals globals)
 #else
 void ArenaPoll(Globals globals)
 {
-  double size;
+  Arena arena;
+  Clock start;
+  Count quanta;
+  Size tracedSize;
+  double nextPollThreshold = 0.0;
 
   AVERT(Globals, globals);
 
   if (globals->clamped)
     return;
-  size = globals->fillMutatorSize;
-  if (globals->insidePoll || size < globals->pollThreshold)
+  if (globals->insidePoll)
+    return;
+  if(globals->fillMutatorSize < globals->pollThreshold)
     return;
 
   globals->insidePoll = TRUE;
 
-  (void)ArenaStep(globals, 0.0, 0.0);
+  /* fillMutatorSize has advanced; call TracePoll enough to catch up. */
+  arena = GlobalsArena(globals);
+  start = ClockNow();
+  quanta = 0;
+  while(globals->pollThreshold <= globals->fillMutatorSize) {
+    tracedSize = TracePoll(globals);
+
+    if(tracedSize == 0) {
+      /* No work to do.  Sleep until NOW + a bit. */
+      nextPollThreshold = globals->fillMutatorSize + ArenaPollALLOCTIME;
+    } else {
+      /* We did one quantum of work; consume one unit of 'time'. */
+      quanta += 1;
+      arena->tracedSize += tracedSize;
+      nextPollThreshold = globals->pollThreshold + ArenaPollALLOCTIME;
+    }
+
+    /* Advance pollThreshold; check: enough precision? */
+    AVER(nextPollThreshold > globals->pollThreshold);
+    globals->pollThreshold = nextPollThreshold;
+  }
+
+  /* Don't count time spent checking for work, if there was no work to do. */
+  if(quanta > 0) {
+    arena->tracedTime += (ClockNow() - start) / (double) ClocksPerSec();
+  }
+
+  AVER(globals->fillMutatorSize < globals->pollThreshold);
 
   globals->insidePoll = FALSE;
 }
@@ -714,7 +746,6 @@ static Bool arenaShouldCollectWorld(Arena arena,
 
 Bool ArenaStep(Globals globals, double interval, double multiplier)
 {
-  double size;
   Size scanned;
   Bool stepped;
   Clock start, end, now;
@@ -756,10 +787,6 @@ Bool ArenaStep(Globals globals, double interval, double multiplier)
     arena->tracedTime += (now - start) / (double) clocks_per_sec;
   }
 
-  size = globals->fillMutatorSize;
-  globals->pollThreshold = size + ArenaPollALLOCTIME;
-  AVER(globals->pollThreshold > size); /* enough precision? */
-
   return stepped;
 }
 
diff --git a/mps/code/zcoll.c b/mps/code/zcoll.c
index 373e60ec2c3..9bc9e931884 100644
--- a/mps/code/zcoll.c
+++ b/mps/code/zcoll.c
@@ -704,7 +704,9 @@ int main(int argc, char **argv)
   /* 16<<20 == 16777216 == 16 Mebibyte */
 
   /* 1<<19 == 524288 == 1/2 Mebibyte */
-  testscriptA("Arena(size 524288), Make(keep-1-in 5, keep 50000, rootspace 30000, sizemethod 1), Collect.");
+  /* This is bogus!  sizemethod 1 can make a 300,000-slot dylan vector, ie. 1.2MB. */
+  /* Try 100MB arena */
+  testscriptA("Arena(size 100000000), Make(keep-1-in 5, keep 50000, rootspace 30000, sizemethod 1), Collect.");
 
   /* LSP -- Large Segment Padding (job001811)
    *
diff --git a/mps/tool/test-runner.py b/mps/tool/test-runner.py
index 2ca61d35580..d3f5e2df932 100755
--- a/mps/tool/test-runner.py
+++ b/mps/tool/test-runner.py
@@ -64,7 +64,7 @@ def mpsplatformcode() :
   # Here, we simplify and get it right for Windows and Macs.
   try :
     compiler = {'xc':'gc',
-                'w3':'mv',
+                'w3':'m9',
                }[os]
   except :
     pass
@@ -79,7 +79,7 @@ mpsplatform = mpsplatformcode()
 make = ''
 if mpsplatform[4:6] == 'gc' :
   make = "make -r -f %s.gmk VARIETY=%%s %%s >> %%s" % mpsplatform
-elif mpsplatform[4:6] == 'mv' :
+elif mpsplatform[4:6] == 'm9' :
   make = "nmake /f %s.nmk VARIETY=%%s %%s.exe >>%%s" % mpsplatform
 
 run = ''
@@ -119,6 +119,7 @@ runtestlist([
     "awlut",
     "awluthe",
     "mpsicv",
+    "zcoll",
     "zmess",
     "messtest",
  ], ["we", "hi", "di", "ci"], testout)