diff --git a/postgresql/cutover/test/pgha-dryrun.yaml b/postgresql/cutover/test/pgha-dryrun.yaml
index fae0e76..44f6d5a 100644
--- a/postgresql/cutover/test/pgha-dryrun.yaml
+++ b/postgresql/cutover/test/pgha-dryrun.yaml
@@ -12,6 +12,11 @@
 #
 # Deploy:   docker stack deploy -c <this file> pgha-test
 # Teardown: docker stack rm pgha-test && rm -rf /volume1/docker/PostgreSQL/dryrun
+#
+# NOTE: command: blocks use $$(...) not $(...) — Compose's own variable
+# interpolation parses $( as an attempted ${VAR} reference and fails with
+# "invalid interpolation format" / "you may need to escape any $ with
+# another $". $$ escapes to a literal $ for the shell at runtime.
 # ─────────────────────────────────────────────────────────────────────────
 version: "3.6"
 
@@ -115,10 +120,10 @@ services:
       - /bin/sh
       - -c
       - |
-        export PGPASSWORD_SUPERUSER="$(cat /run/secrets/postgresql_password)"
-        export PGPASSWORD_STANDBY="$(cat /run/secrets/postgresql_replication_password)"
-        export PATRONI_RESTAPI_PASSWORD="$(cat /run/secrets/postgresql_patroni_password)"
-        export CLONE_PASSWORD="$(cat /run/secrets/postgresql_password)"
+        export PGPASSWORD_SUPERUSER="$$(cat /run/secrets/postgresql_password)"
+        export PGPASSWORD_STANDBY="$$(cat /run/secrets/postgresql_replication_password)"
+        export PATRONI_RESTAPI_PASSWORD="$$(cat /run/secrets/postgresql_patroni_password)"
+        export CLONE_PASSWORD="$$(cat /run/secrets/postgresql_password)"
         exec /bin/sh /launch.sh init
     environment:
       SCOPE: pgha-test
@@ -153,10 +158,10 @@ services:
       - /bin/sh
       - -c
       - |
-        export PGPASSWORD_SUPERUSER="$(cat /run/secrets/postgresql_password)"
-        export PGPASSWORD_STANDBY="$(cat /run/secrets/postgresql_replication_password)"
-        export PATRONI_RESTAPI_PASSWORD="$(cat /run/secrets/postgresql_patroni_password)"
-        export CLONE_PASSWORD="$(cat /run/secrets/postgresql_password)"
+        export PGPASSWORD_SUPERUSER="$$(cat /run/secrets/postgresql_password)"
+        export PGPASSWORD_STANDBY="$$(cat /run/secrets/postgresql_replication_password)"
+        export PATRONI_RESTAPI_PASSWORD="$$(cat /run/secrets/postgresql_patroni_password)"
+        export CLONE_PASSWORD="$$(cat /run/secrets/postgresql_password)"
         exec /bin/sh /launch.sh init
     environment:
       SCOPE: pgha-test