diff --git a/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/h2/V7.6_2023.09.18__workspaceitem_add_item_id_unique_constraint.sql b/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/h2/V7.6_2023.09.18__workspaceitem_add_item_id_unique_constraint.sql
deleted file mode 100644
index 2ad43d45e071..000000000000
--- a/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/h2/V7.6_2023.09.18__workspaceitem_add_item_id_unique_constraint.sql
+++ /dev/null
@@ -1,9 +0,0 @@
---
--- The contents of this file are subject to the license and copyright
--- detailed in the LICENSE and NOTICE files at the root of the source
--- tree and available online at
---
--- http://www.dspace.org/license/
---
-
-ALTER TABLE workspaceitem ADD CONSTRAINT unique_item_id UNIQUE(item_id);
diff --git a/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/h2/V7.6_2024.12.17__workspaceitem_add_item_id_unique_constraint.sql b/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/h2/V7.6_2024.12.17__workspaceitem_add_item_id_unique_constraint.sql
new file mode 100644
index 000000000000..d2b7de7dc374
--- /dev/null
+++ b/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/h2/V7.6_2024.12.17__workspaceitem_add_item_id_unique_constraint.sql
@@ -0,0 +1,21 @@
+--
+-- The contents of this file are subject to the license and copyright
+-- detailed in the LICENSE and NOTICE files at the root of the source
+-- tree and available online at
+--
+-- http://www.dspace.org/license/
+--
+
+-- In the workspaceitem table, if there are multiple rows referring to the same item ID, keep only the first of them.
+WITH dedup AS (
+    SELECT item_id, MIN(workspace_item_id) AS workspace_item_id
+    FROM workspaceitem
+    GROUP BY item_id
+    HAVING COUNT(workspace_item_id) > 1
+)
+DELETE FROM workspaceitem
+    USING dedup
+WHERE workspaceitem.item_id = dedup.item_id AND workspaceitem.workspace_item_id <> dedup.workspace_item_id;
+
+-- Identify which rows have duplicates, and compute their replacements.
+ALTER TABLE workspaceitem ADD CONSTRAINT unique_item_id UNIQUE(item_id);
diff --git a/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/postgres/V7.6_2023.09.18__workspaceitem_add_item_id_unique_constraint.sql b/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/postgres/V7.6_2023.09.18__workspaceitem_add_item_id_unique_constraint.sql
deleted file mode 100644
index 2ad43d45e071..000000000000
--- a/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/postgres/V7.6_2023.09.18__workspaceitem_add_item_id_unique_constraint.sql
+++ /dev/null
@@ -1,9 +0,0 @@
---
--- The contents of this file are subject to the license and copyright
--- detailed in the LICENSE and NOTICE files at the root of the source
--- tree and available online at
---
--- http://www.dspace.org/license/
---
-
-ALTER TABLE workspaceitem ADD CONSTRAINT unique_item_id UNIQUE(item_id);
diff --git a/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/postgres/V7.6_2024.12.17__workspaceitem_add_item_id_unique_constraint.sql b/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/postgres/V7.6_2024.12.17__workspaceitem_add_item_id_unique_constraint.sql
new file mode 100644
index 000000000000..20eb0f9119d3
--- /dev/null
+++ b/dspace-api/src/main/resources/org/dspace/storage/rdbms/sqlmigration/postgres/V7.6_2024.12.17__workspaceitem_add_item_id_unique_constraint.sql
@@ -0,0 +1,21 @@
+--
+-- The contents of this file are subject to the license and copyright
+-- detailed in the LICENSE and NOTICE files at the root of the source
+-- tree and available online at
+--
+-- http://www.dspace.org/license/
+--
+
+-- In the workspaceitem table, if there are multiple rows referring to the same item ID, keep only the first of them.
+WITH dedup AS (
+    SELECT item_id, MIN(workspace_item_id) AS workspace_item_id
+    FROM workspaceitem
+    GROUP BY item_id
+    HAVING COUNT(workspace_item_id) > 1
+)
+DELETE FROM workspaceitem
+USING dedup
+WHERE workspaceitem.item_id = dedup.item_id AND workspaceitem.workspace_item_id <> dedup.workspace_item_id;
+
+-- Enforce uniqueness of item_id in workspaceitem table.
+ALTER TABLE workspaceitem ADD CONSTRAINT unique_item_id UNIQUE(item_id);