diff --git a/src/nancy/schema/version0.sql b/src/nancy/schema/version0.sql
index 9bfe3d1..c777ab7 100644
--- a/src/nancy/schema/version0.sql
+++ b/src/nancy/schema/version0.sql
@@ -76,9 +76,22 @@ CREATE TABLE user(id INTEGER PRIMARY KEY NOT NULL,
 -- Stores and files (and directories)
 -- These are the primary objects tracked by nancy.
 -- A store is a directory containing a file called nancy.db (e.g. the dir holding this database)
+-- In order to reliably merge store entries (like when we have converging
+-- dependencies), we need to deduplicate. The machine and path could match, for
+-- example if a database is created in one location then copied elsewhere,
+-- followed by regenerating the original database. In these cases, we would want
+-- to distinguish the new database from the copied one while still being able to
+-- equate two simple copies of a db.
+-- For this we use a UUID generated randomly
+-- by the client. SQLite does not natively support UUIDs but it is stored here
+-- as a string.
+-- Client code should generate random UUIDs in the RFC 4122 variant layout.
+-- https://datatracker.ietf.org/doc/html/rfc4122.html
+-- This is possible in Python by simply calling uuid.uuid4() with no arguments
 CREATE TABLE store (id INTEGER PRIMARY KEY NOT NULL,
     machine INTEGER,
     dbpath TEXT NOT NULL,
+    uuid TEXT NOT NULL, -- str(uuid.uuid4())
     imported BOOL, -- is this the store for the current directory? If not, then it was
     -- imported in order to describe a dependency.
 
diff --git a/tests/test_db.py b/tests/test_db.py
index 589e8e3..7ad04f2 100644
--- a/tests/test_db.py
+++ b/tests/test_db.py
@@ -123,25 +123,29 @@ def test_invalid_user_machine(insert_user):
 
 @pytest.fixture
 def insert_store(insert_machine):
+    import uuid
     cur = insert_machine
     cur.executemany(
         'INSERT INTO store VALUES '
-        '(?, ?, ?, ?)',
+        '(?, ?, ?, ?, ?)',
         [(
             None, #id INTEGER PRIMARY KEY NOT NULL,
             1, #machine INTEGER,
             '/path/to/first/store', #dbpath TEXT NOT NULL,
+            str(uuid.uuid4()), #-- UUID generated by str(uuid.uuid4())
             False, #imported BOOL,
         ), (
             None, #id INTEGER PRIMARY KEY NOT NULL,
             1, #machine INTEGER,
             '/path/to/dependency/store', #dbpath TEXT NOT NULL,
+            str(uuid.uuid4()), #-- UUID generated by str(uuid.uuid4())
             True, #imported BOOL,
         ), (
             None, #id INTEGER PRIMARY KEY NOT NULL,
             2, #machine INTEGER,
             # same path but on a separate machine
             '/path/to/first/store', #dbpath TEXT NOT NULL,
+            str(uuid.uuid4()), #-- UUID generated by str(uuid.uuid4())
             True, #imported BOOL,
         )],
     )