diff --git a/backend/alembic/versions/2026_04_23_0000-0b9c1d2e3f4a_initial_schema.py b/backend/alembic/versions/2026_04_23_0000-0b9c1d2e3f4a_initial_schema.py
index 4b47683..92d0bdf 100644
--- a/backend/alembic/versions/2026_04_23_0000-0b9c1d2e3f4a_initial_schema.py
+++ b/backend/alembic/versions/2026_04_23_0000-0b9c1d2e3f4a_initial_schema.py
@@ -232,9 +232,18 @@ def upgrade() -> None:
     """)
 
     op.execute("""
-    ALTER TABLE item_versions
-        ADD CONSTRAINT IF NOT EXISTS item_versions_item_id_fkey
-        FOREIGN KEY (item_id) REFERENCES document_items(id)
+    DO $$
+    BEGIN
+        IF NOT EXISTS (
+            SELECT 1 FROM information_schema.table_constraints
+            WHERE constraint_name = 'item_versions_item_id_fkey'
+            AND table_name = 'item_versions'
+        ) THEN
+            ALTER TABLE item_versions
+                ADD CONSTRAINT item_versions_item_id_fkey
+                FOREIGN KEY (item_id) REFERENCES document_items(id);
+        END IF;
+    END $$
     """)
 
     op.execute("""