diff --git a/meta-google/recipes-google/networking/files/gbmc-mac-config.sh.in b/meta-google/recipes-google/networking/files/gbmc-mac-config.sh.in
index dce4611..aaa9920 100644
--- a/meta-google/recipes-google/networking/files/gbmc-mac-config.sh.in
+++ b/meta-google/recipes-google/networking/files/gbmc-mac-config.sh.in
@@ -60,13 +60,17 @@
 done
 
 # Write out each MAC override to the runtime networkd configuration
+lower=$(((mac[3] << 16) | (mac[4] << 8) | mac[5]))
 for (( i=0; i<num; i++ )); do
-  if (( mac[5] > 0xff )); then
+  if (( lower > 0xffffff )); then
     echo "MAC assignment too large: ${mac[*]}" >&2
     rc=2
     break
   fi
   for intf in ${num_to_intfs[$i]}; do
+    mac[3]=$(((lower >> 16) & 0xff))
+    mac[4]=$(((lower >> 8) & 0xff))
+    mac[5]=$(((lower >> 0) & 0xff))
     macstr=$(printf '%02x:%02x:%02x:%02x:%02x:%02x' "${mac[@]}")
     echo "Setting $intf to $macstr" >&2
     for override in /run/systemd/network/{00,}-bmc-$intf.network.d; do
@@ -85,7 +89,7 @@
       echo "Setting MAC($macstr) on $intf failed" >&2
     fi
   done
-  (( ++mac[5] ))
+  (( ++lower ))
 done
 
 exit $rc