diff --git a/cmd/bent/README.md b/cmd/bent/README.md
index d594e75..2d55f62 100644
--- a/cmd/bent/README.md
+++ b/cmd/bent/README.md
@@ -6,6 +6,8 @@
 
 Installation:
 ```go get github.com/dr2chase/bent```
+Requires commands `rsync` and `/usr/bin/time`.
+
 Also depends on burntsushi/toml, and expects that Docker is installed and available on the command line.
 You can avoid the need for Docker with the `-U` command line flag, if you're okay with running benchmarks outside containers.
 Alternately, if you wish to only run those benchmarks that can be compiled into a container (this is platform-dependent)
diff --git a/cmd/bent/configs/benchmarks-50.toml b/cmd/bent/configs/benchmarks-50.toml
index 502d1fc..2ce36be 100644
--- a/cmd/bent/configs/benchmarks-50.toml
+++ b/cmd/bent/configs/benchmarks-50.toml
@@ -177,6 +177,7 @@
   Name = "capnproto2"
   Repo = "zombiezen.com/go/capnproto2/"
   Benchmarks = "Benchmark(TextMovementBetweenSegments|Growth_MultiSegment)"
+  GcEnv = ["GO111MODULE=on"]
 
 [[Benchmarks]]
   Name = "uber_zap"
diff --git a/cmd/bent/configs/benchmarks-all.toml b/cmd/bent/configs/benchmarks-all.toml
index 3757fa2..5c6be49 100644
--- a/cmd/bent/configs/benchmarks-all.toml
+++ b/cmd/bent/configs/benchmarks-all.toml
@@ -190,6 +190,7 @@
   Name = "capnproto2"
   Repo = "zombiezen.com/go/capnproto2/"
   Benchmarks = "Benchmark"
+  GcEnv = ["GO111MODULE=on"]
 
 [[Benchmarks]]
   Name = "uber_zap"
diff --git a/cmd/bent/scripts/benchsize b/cmd/bent/scripts/benchsize
index 5f9e382..4b48be1 100755
--- a/cmd/bent/scripts/benchsize
+++ b/cmd/bent/scripts/benchsize
@@ -2,30 +2,36 @@
 
 tmp=tmp-bench-size-$$
 
-x=`which gsize`
-
-if [ "x$x" = "x" ] ; then
-	size -A "$1" > $tmp
-else
-	"$x" -A "$1" > $tmp
+if [ `uname` = "Darwin" ] ; then
+	awkcommand='{print $3}'
+	size -m "$1" > $tmp
+ else
+	x=`which gsize`
+	awkcommand='{print $2}'
+	if [ "x$x" = "x" ] ; then
+		size -A "$1" > $tmp
+	else
+		"$x" -A "$1" > $tmp
+	fi
 fi
 
 
+# note total is different -- always $2
+total=`egrep -i '^total' $tmp | awk -Wposix '{print $2}'`
 
-total=`grep Total $tmp | awk '{print $2}'`
-text=`egrep [^a-z]text[^a-z] $tmp | awk '{print $2}'`
-gopclntab=`grep gopclntab $tmp | awk '{print $2}'`
-rodata=`grep rodata $tmp | awk '{print $2}'`
-data=`egrep [^a-z]data[^a-z._] $tmp | awk '{print $2}'`
+text=`egrep [^a-z]text[^a-z] $tmp | awk -Wposix "$awkcommand"`
+gopclntab=`grep gopclntab $tmp | awk -Wposix "$awkcommand"`
+rodata=`grep rodata $tmp | awk -Wposix "$awkcommand"`
+data=`egrep [^a-z]data[^a-z._] $tmp | awk -Wposix "$awkcommand"`
 
-zdebug_info=`grep zdebug_info $tmp | awk '{print $2}'`
-zdebug_loc=`grep zdebug_loc $tmp | awk '{print $2}'`
-zdebug_line=`grep zdebug_line $tmp | awk '{print $2}'`
-zdebug_ranges=`grep zdebug_ranges $tmp | awk '{print $2}'`
-zdebug_frame=`grep zdebug_frame $tmp | awk '{print $2}'`
-zdebug_abbrev=`grep zdebug_abbrev $tmp | awk '{print $2}'`
-zdebug_pubname=`grep zdebug_pubname $tmp | awk '{print $2}'`
-zdebug_pubtype=`grep zdebug_pubtype $tmp | awk '{print $2}'`
+zdebug_info=`grep zdebug_info $tmp | awk -Wposix "$awkcommand"`
+zdebug_loc=`grep zdebug_loc $tmp | awk -Wposix "$awkcommand"`
+zdebug_line=`grep zdebug_line $tmp | awk -Wposix "$awkcommand"`
+zdebug_ranges=`grep zdebug_ranges $tmp | awk -Wposix "$awkcommand"`
+zdebug_frame=`grep zdebug_frame $tmp | awk -Wposix "$awkcommand"`
+zdebug_abbrev=`grep zdebug_abbrev $tmp | awk -Wposix "$awkcommand"`
+zdebug_pubname=`grep zdebug_pubname $tmp | awk -Wposix "$awkcommand"`
+zdebug_pubtype=`grep zdebug_pubtype $tmp | awk -Wposix "$awkcommand"`
 
 zdebug_abbrev=${zdebug_abbrev:-0}
 zdebug_pubname=${zdebug_pubname:-0}
@@ -40,7 +46,6 @@
 echo "Benchmark${2}_rodata" 1 ${rodata} rodata-bytes
 echo "Benchmark${2}_pclntab" 1 ${gopclntab} pclntab-bytes
 
-
 zdebug=`expr ${zdebug_info} + ${zdebug_loc} + ${zdebug_line} + ${zdebug_ranges} + ${zdebug_frame} + ${zdebug_abbrev} + ${zdebug_pubname} + ${zdebug_pubtype}`
 
 echo "Benchmark${2}_zdebug_total" 1 ${zdebug} zdebug-bytes