diff --git a/src/platform/unix/BuildLinuxImage.sh.in b/src/platform/unix/BuildLinuxImage.sh.in
index 168e8c7a0..4b5457a0d 100644
--- a/src/platform/unix/BuildLinuxImage.sh.in
+++ b/src/platform/unix/BuildLinuxImage.sh.in
@@ -1,7 +1,13 @@
 #!/bin/bash
 
+# Our sysctl call may be run as normal user,
+# but /sbin is not always in normal users' PATH.
+if [[ -f /sbin/sysctl && -x /sbin/sysctl ]]; then sysctl_bin=/sbin/sysctl
+else sysctl_bin=sysctl  # If not found in sbin, hope
+fi
+
 export ROOT=`pwd`
-export NCORES=`sysctl -n hw.ncpu`
+export NCORES=`"$sysctl_bin" -n hw.ncpu`
 
 while getopts ":ih" opt; do
   case ${opt} in