diff --git a/balena-entrypoint.sh b/balena-entrypoint.sh
index 20ccd65..b388984 100755
--- a/balena-entrypoint.sh
+++ b/balena-entrypoint.sh
@@ -2,14 +2,6 @@
 
 set -e
 
-# copies all the data from $1 to $2
-restore_volume () {
-    echo "=== Restoring data volume structure"
-    find "$1" -maxdepth 1 \
-        ! -path "$1" \
-        | xargs mv -t "$2"
-}
-
 # install the old version of Postgres, required when doing an upgrade
 install_old_version () {
     if [ ! -d "/usr/lib/postgresql/$1/bin" ]; then
@@ -41,37 +33,49 @@ die_with_message () {
 
 # set our target version
 TARGET_VERSION="$PG_MAJOR"
+PGDATANEW="${PGDATA}/${TARGET_VERSION}"
+
+migrate_pgdata_root_if_needed () {
+    # perform a one-time migration from storing data under $PGDATA root,
+    # to storing it under $PGDATA/$PG_VERSION
+    if [ -f "${PGDATA}/PG_VERSION" ]; then
+        local version="$(cat "${PGDATA}/PG_VERSION")"
+        if [ ! -d "${PGDATA}/${version}" ]; then
+            create_postgres_data_dir "${PGDATA}/${version}"
+            echo "=== Moving existing data to directory "${PGDATA}/${version}""
+            find "$PGDATA" -maxdepth 1 \
+                ! -path "$PGDATA" \
+                ! -path "${PGDATA}/${version}*" \
+                | xargs mv -t "${PGDATA}/${version}"
+        fi
+    fi
+}
 
-# ensure we have a versioned data directory
-[ -d "${PGDATA}/${TARGET_VERSION}" ] || create_postgres_data_dir "${PGDATA}/${TARGET_VERSION}"
-
-# check for Postgres data in the root of the $PGDATA directory
-if [ -f "${PGDATA}/PG_VERSION" ]; then
-    SOURCE_VERSION="$(cat ${PGDATA}/PG_VERSION)"
+find_source_version () {
+    # find our source version by looking for a PG_VERSION file
+    # in every directory under $PGDATA
+    for src in $(find "$PGDATA" -maxdepth 2 -type f -name 'PG_VERSION' | sort -rn); do
+        local version="$(cat "$src")"
+        if [ "$version" -ne "$TARGET_VERSION" ]; then
+            SOURCE_VERSION="$version"
+            PGDATAOLD="$(dirname "$src")" # drop 'PG_VERSION' from path
+            break
+        fi
+    done
+}
 
+perform_migration_if_needed () {
     # does the data need upgrading?
-    if [ "$SOURCE_VERSION" -ne "$TARGET_VERSION" ]; then
+    if [ -n "${SOURCE_VERSION}" ]; then
         echo "=== Upgrading data from v${SOURCE_VERSION} to v${TARGET_VERSION}"
 
-        PGDATAOLD="${PGDATA}/${SOURCE_VERSION}"
-        PGDATANEW="${PGDATA}/${TARGET_VERSION}"
         PGBINOLD="/usr/lib/postgresql/$SOURCE_VERSION/bin"
         PGBINNEW="/usr/lib/postgresql/$TARGET_VERSION/bin"
 
         echo "=== Installing tools for Postgres v${SOURCE_VERSION}"
         install_old_version "$SOURCE_VERSION"
 
-        echo "=== Moving existing data to ${PGDATAOLD}"
-        create_postgres_data_dir "${PGDATAOLD}"
-        find "$PGDATA" -maxdepth 1 \
-            ! -path "$PGDATA" \
-            ! -path "$PGDATAOLD*" \
-            | xargs mv -t "${PGDATAOLD}"
-
-        trap "restore_volume ${PGDATAOLD} ${PGDATA}" ERR
-
         echo "=== Initializing new data directory ${PGDATANEW}"
-        rm -rf "${PGDATANEW}"
         create_postgres_data_dir "${PGDATANEW}"
         gosu postgres initdb -D "$PGDATANEW" -U "$POSTGRES_USER" $POSTGRES_INITDB_ARGS
 
@@ -95,16 +99,21 @@ if [ -f "${PGDATA}/PG_VERSION" ]; then
         echo "=== Restoring configuration files"
         cp "${PGDATAOLD}/pg_hba.conf" "${PGDATANEW}/pg_hba.conf"
         cp "${PGDATAOLD}/pg_ident.conf" "${PGDATANEW}/pg_ident.conf"
-    else
-        echo "=== Moving existing data to directory "${PGDATA}/${TARGET_VERSION}""
-        find "$PGDATA" -maxdepth 1 \
-            ! -path "$PGDATA" \
-            | xargs mv -t "${PGDATA}/${TARGET_VERSION}"
+
+        echo "=== Migration succeeded; removing old data directory"
+        rm -rf "${PGDATAOLD}"
     fi
-fi
+}
+
+migrate_pgdata_root_if_needed
+find_source_version
+perform_migration_if_needed
+
+# ensure we have a versioned data directory
+[ -d "${PGDATANEW}" ] || create_postgres_data_dir "${PGDATANEW}"
 
 # set our runtime data directory to the target version
-export PGDATA="${PGDATA}/${TARGET_VERSION}"
+export PGDATA="${PGDATANEW}"
 
 # run the existing Postgres entrypoint script
 . /usr/local/bin/docker-entrypoint.sh