diff --git a/schemas/ispyb/updates/2025_05_28_BLSession_icatId.sql b/schemas/ispyb/updates/2025_05_28_BLSession_icatId.sql
new file mode 100644
index 0000000..eea68d9
--- /dev/null
+++ b/schemas/ispyb/updates/2025_05_28_BLSession_icatId.sql
@@ -0,0 +1,6 @@
+INSERT IGNORE INTO SchemaStatus (scriptName, schemaStatus) VALUES ('2025_05_28_BLSession_icatId.sql', 'ONGOING');
+
+ALTER TABLE BLSession
+  ADD icatId int(11) unsigned COMMENT 'The internal ICAT ID for this BLSession';
+
+UPDATE SchemaStatus SET schemaStatus = 'DONE' WHERE scriptName = '2025_05_28_BLSession_icatId.sql';