diff --git a/flash/factory.common b/flash/factory.common
index ce2d570e59ff028fe789157e19a2897b9643788f..9131a7d209d506f8a6eb45c4bf8ec3da5377ff17 100755
--- a/flash/factory.common
+++ b/flash/factory.common
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-set -e
+set -euo pipefail
 
 # Paths/files
 ROOT_DIR="$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
@@ -70,6 +70,9 @@ fi
 # Check for connected phone
 find_device() {
   echo "INFO: Looking for connected device(s)..."
+  PRODUCT="${PRODUCT:-unknown}"
+  PRODUCT_ID="${PRODUCT_ID:-unknown}"
+  PRODUCT_ID_OLD="${PRODUCT_ID_OLD:-unknown}"
   DEVICE_FOUND="false"
   while [ ${DEVICE_FOUND} = "false" ]
   do
@@ -80,8 +83,18 @@ find_device() {
       # Checking the product ID
       PRODUCT_STRING=$("${FASTBOOT_BIN}" -s "${sn}" getvar product 2>&1)
       # Add serial, if product matches
-      if [[ ${PRODUCT_STRING} == *"${PRODUCT_ID}"* ]] || [[ ${PRODUCT_STRING} == *"${PRODUCT_ID_OLD}"* ]]
-      then
+      matched=false
+      if [[ "${PRODUCT_ID}" != "unknown" ]]; then
+        if [[ ${PRODUCT_STRING} == *"${PRODUCT_ID}"* ]]; then
+          matched=true
+        fi
+      fi
+      if [[ "${PRODUCT_ID_OLD}" != "unknown" ]]; then
+        if [[ ${PRODUCT_STRING} == *"${PRODUCT_ID_OLD}"* ]]; then
+          matched=true
+        fi
+      fi
+      if [[ "${matched}" == "true" ]]; then
         serial_numbers="${serial_numbers} $sn"
       fi
     done
@@ -161,6 +174,16 @@ fi
 # Common flash function to be called from device flash script
 flash_factory() {
   # Begin with some OS checks and variable definition
+  USE_FASTBOOTD="${USE_FASTBOOTD:-false}"
+  FW_BL_RESTART="${FW_BL_RESTART:-false}"
+  CLEAN_FLASH="${CLEAN_FLASH:-false}"
+  VIRTUAL_AB="${VIRTUAL_AB:-false}"
+  FLASH_AB_FW_IMGS="${FLASH_AB_FW_IMGS:-}"
+  FLASH_A_FW_IMGS="${FLASH_A_FW_IMGS:-}"
+  FLASH_AB_IMGS="${FLASH_AB_IMGS:-}"
+  FLASH_A_IMGS="${FLASH_A_IMGS:-}"
+  ERASE_IMGS="${ERASE_IMGS:-}"
+  FORMAT_IMGS="${FORMAT_IMGS:-}"
   os_checks
 
   # Call function to look for device(s)
@@ -215,7 +238,7 @@ then
     for BLOB in $2;
     do
       PARTITION="${BLOB%%:*}"
-      IMAGE=$(echo $BLOB | cut -s -d : -f 2)
+      IMAGE=$(echo "$BLOB" | cut -s -d : -f 2)
 
       if [[ "$PARTITION" = "userdata" && "${CLEAN_FLASH}" != "true" ]]
       then
@@ -234,7 +257,7 @@ then
     for BLOB in $2;
     do
       PARTITION="${BLOB%%:*}"
-      IMAGE=$(echo $BLOB | cut -s -d : -f 2)
+      IMAGE=$(echo "$BLOB" | cut -s -d : -f 2)
 
       flash_image_ab_or_abort "${1}" "${PARTITION}" "${IMAGES_DIR}/${IMAGE:-$PARTITION.img}"
     done