diff --git a/setup/preflight.sh b/setup/preflight.sh
index 742d6db9..afa43027 100644
--- a/setup/preflight.sh
+++ b/setup/preflight.sh
@@ -19,8 +19,8 @@ fi
 
 # Check that we have enough memory. Skip the check if we appear to be
 # running inside of Vagrant, because that's really just for testing.
-TOTAL_PHYSICAL_MEM=$(free -m | grep ^Mem: | sed "s/^Mem: *\([0-9]*\).*/\1/")
-if [ $TOTAL_PHYSICAL_MEM -lt 768 ]; then
+TOTAL_PHYSICAL_MEM=$(head -n 1 /proc/meminfo | awk '{print $2}')
+if [ $TOTAL_PHYSICAL_MEM -lt 786432 ]; then
 if [ ! -d /vagrant ]; then
 	echo "Your Mail-in-a-Box needs more than $TOTAL_PHYSICAL_MEM MB RAM."
 	echo "Please provision a machine with at least 768 MB, 1 GB recommended."