diff --git a/test/iceberg_data_files.sh b/test/iceberg_data_files.sh
index f8fac4e37..fb53b1b79 100755
--- a/test/iceberg_data_files.sh
+++ b/test/iceberg_data_files.sh
@@ -288,23 +288,34 @@ check "a table with no current snapshot yields no data files" \
 	"$(q "SELECT count(*) FROM pgcolumnar.iceberg_data_files('$NOSNAP')")" "0"
 
 # ---- privilege: needs pg_read_server_files ---------------------------------
-# The role gets USAGE on the schema and EXECUTE on the function, so the refusal is
-# the function's own gate. Without them the 42501 is "permission denied for schema
-# pgcolumnar", the function never runs, and the arm cannot fail on the gate it names.
+# The role gets USAGE on the schema, so the refusal is the function's own gate (EXECUTE
+# it already has, through PUBLIC). Without USAGE the 42501 is "permission denied for
+# schema pgcolumnar" and the function never runs, so the arm requires the gate's own
+# message, naming pg_read_server_files, and not only the SQLSTATE they share.
 DROP_UNPRIV="DO \$\$BEGIN IF EXISTS (SELECT FROM pg_roles WHERE rolname = 'icedf_unpriv')
 	THEN EXECUTE 'DROP OWNED BY icedf_unpriv'; END IF; END\$\$;
 DROP ROLE IF EXISTS icedf_unpriv;"
 psql_run "$DROP_UNPRIV
 CREATE ROLE icedf_unpriv LOGIN;
-GRANT USAGE ON SCHEMA pgcolumnar TO icedf_unpriv;
-GRANT EXECUTE ON FUNCTION pgcolumnar.iceberg_data_files TO icedf_unpriv;"
-check "an unprivileged role is refused (42501)" \
-	"$(env PATH="$PGC_BINDIR:$PATH" psql -h 127.0.0.1 -p "$PGC_PORT" -U icedf_unpriv -d "$PGC_DB" \
-		-qtA 2>&1 <<SQL | sed -n 's/^ERROR:  \([0-9A-Z]\{5\}\).*/\1/p' | head -1
-\\set VERBOSITY sqlstate
+GRANT USAGE ON SCHEMA pgcolumnar TO icedf_unpriv;"
+icedf_out="$(env PATH="$PGC_BINDIR:$PATH" psql -h 127.0.0.1 -p "$PGC_PORT" -U icedf_unpriv -d "$PGC_DB" \
+	-qtA 2>&1 <<SQL
+\\set VERBOSITY verbose
 SELECT count(*) FROM pgcolumnar.iceberg_data_files('$MD');
 SQL
-)" "42501"
+)"
+# Only the ERROR line's message counts, as the twin reads message_primary: a role
+# named in a HINT or DETAIL line is not the gate saying so.
+icedf_err="${icedf_out#*ERROR:  }"; icedf_err="${icedf_err%%$'\n'*}"
+case "$icedf_out" in
+	*"ERROR:  "*) ;;
+	*) icedf_err="" ;;
+esac
+case "$icedf_err" in
+	"42501: "*pg_read_server_files*) icedf_got=42501 ;;
+	*) icedf_got="${icedf_out%%$'\n'*}"; icedf_got="${icedf_got:-no output}" ;;
+esac
+check "an unprivileged role is refused (42501)" "$icedf_got" "42501"
 psql_run "$DROP_UNPRIV"
 
 pgc_summary
diff --git a/test/pytest/test_iceberg_data_files.py b/test/pytest/test_iceberg_data_files.py
index 00967dd45..5974528ca 100644
--- a/test/pytest/test_iceberg_data_files.py
+++ b/test/pytest/test_iceberg_data_files.py
@@ -184,19 +184,33 @@ def _one(dsn, sql, *params):
         return _failed(exc)
 
 
-def _sqlstate(dsn, path, role=None):
-    """The SQLSTATE listing `path` fails with, or "ok", in a session of its own;
-    `role`, if given, is SET first. A failure with no SQLSTATE is a failed reading."""
+def _sqlstate(dsn, path):
+    """The SQLSTATE listing `path` fails with, or "ok", in a session of its own. A
+    failure with no SQLSTATE is a failed reading."""
     try:
         with psycopg.connect(dsn, autocommit=True) as conn:
-            if role:
-                conn.execute(f"SET ROLE {role}")
             conn.execute("SELECT * FROM pgcolumnar.iceberg_data_files(%s)", (str(path),)).fetchall()
             return "ok"
     except psycopg.Error as exc:
         return exc.sqlstate or _failed(exc)
 
 
+def _gate_refusal(dsn, path, role):
+    """"42501" when `role` listing `path` is refused by the pg_read_server_files gate;
+    otherwise what happened instead, or the failed reading."""
+    try:
+        with psycopg.connect(dsn, autocommit=True) as conn:
+            conn.execute(f"SET ROLE {role}")
+            conn.execute("SELECT * FROM pgcolumnar.iceberg_data_files(%s)", (str(path),)).fetchall()
+            return "ok"
+    except psycopg.Error as exc:
+        if not exc.sqlstate:
+            return _failed(exc)
+        primary = exc.diag.message_primary or ""
+        return "42501" if exc.sqlstate == "42501" and "pg_read_server_files" in primary \
+            else f"{exc.sqlstate}: {primary}"
+
+
 def _run(dsn, *stmts):
     """Statements in a session of their own -> None, or the failed reading."""
     try:
@@ -208,14 +222,14 @@ def _run(dsn, *stmts):
         return _failed(exc)
 
 
-# The unprivileged role reaches the function: USAGE on the schema and EXECUTE on the
-# function, or its 42501 is the schema's and the pg_read_server_files gate never runs.
+# The unprivileged role reaches the function: USAGE on the schema (EXECUTE it has
+# through PUBLIC), or its 42501 is the schema's and the pg_read_server_files gate never
+# runs. The arm requires the gate's own message, not only the SQLSTATE they share.
 DROP_UNPRIV = ("DO $$BEGIN IF EXISTS (SELECT FROM pg_roles WHERE rolname = 'icedf_unpriv') "
                "THEN EXECUTE 'DROP OWNED BY icedf_unpriv'; END IF; END$$",
                "DROP ROLE IF EXISTS icedf_unpriv")
 MAKE_UNPRIV = DROP_UNPRIV + ("CREATE ROLE icedf_unpriv LOGIN",
-                             "GRANT USAGE ON SCHEMA pgcolumnar TO icedf_unpriv",
-                             "GRANT EXECUTE ON FUNCTION pgcolumnar.iceberg_data_files TO icedf_unpriv")
+                             "GRANT USAGE ON SCHEMA pgcolumnar TO icedf_unpriv")
 
 
 def _alive(pgc_cluster):
@@ -313,7 +327,7 @@ def ice(pgc_cluster, tmp_path_factory):
         got[f"entry {k}"] = _sqlstate(dsn, entries[k])
     got["alive entries"] = _recovered(pgc_cluster, _alive(pgc_cluster))
     got["no snapshot"] = _one(dsn, lst.format("count(*)"), str(nosnap))
-    got["unprivileged"] = _run(dsn, *MAKE_UNPRIV) or _sqlstate(dsn, md, role="icedf_unpriv")
+    got["unprivileged"] = _run(dsn, *MAKE_UNPRIV) or _gate_refusal(dsn, md, "icedf_unpriv")
     try:
         yield got
     finally: