diff --git a/README.md b/README.md
index 71be938..a246b5f 100644
--- a/README.md
+++ b/README.md
@@ -205,6 +205,10 @@ The following environment variables are supported:
 
     If set, then instead of working through the numeric stages in order, this list will be followed. For example setting to `"stage0 stage1 mystage stage2"` will run the contents of `mystage` before stage2. Note that quotes are needed around the list. An absolute or relative path can be given for stages outside the pi-gen directory.
 
+ * `EXPORT_CONFIG_DIR` (Default: `$BASE_DIR/export-image`)
+
+    If set, use this directory path as the location of scripts to run when generating images. An absolute or relative path can be given for a location outside the pi-gen directory.
+
 A simple example for building Raspberry Pi OS:
 
 ```bash
diff --git a/build.sh b/build.sh
index a96f4e4..4864dd6 100755
--- a/build.sh
+++ b/build.sh
@@ -301,6 +301,13 @@ log "Begin ${BASE_DIR}"
 STAGE_LIST=${STAGE_LIST:-${BASE_DIR}/stage*}
 export STAGE_LIST
 
+EXPORT_CONFIG_DIR=$(realpath "${EXPORT_CONFIG_DIR:-"${BASE_DIR}/export-image"}")
+if [ ! -d "${EXPORT_CONFIG_DIR}" ]; then
+	echo "EXPORT_CONFIG_DIR invalid: ${EXPORT_CONFIG_DIR} does not exist"
+	exit 1
+fi
+export EXPORT_CONFIG_DIR
+
 for STAGE_DIR in $STAGE_LIST; do
 	STAGE_DIR=$(realpath "${STAGE_DIR}")
 	run_stage
@@ -308,7 +315,7 @@ done
 
 CLEAN=1
 for EXPORT_DIR in ${EXPORT_DIRS}; do
-	STAGE_DIR=${BASE_DIR}/export-image
+	STAGE_DIR=${EXPORT_CONFIG_DIR}
 	# shellcheck source=/dev/null
 	source "${EXPORT_DIR}/EXPORT_IMAGE"
 	EXPORT_ROOTFS_DIR=${WORK_DIR}/$(basename "${EXPORT_DIR}")/rootfs