diff --git a/datasette/database.py b/datasette/database.py
index d1217e18..0a0c104a 100644
--- a/datasette/database.py
+++ b/datasette/database.py
@@ -128,6 +128,7 @@ class Database:
         conn = None
         try:
             conn = self.connect(write=True)
+            self.ds._prepare_connection(conn, self.name)
         except Exception as e:
             conn_exception = e
         while True:
diff --git a/tests/test_internals_database.py b/tests/test_internals_database.py
index a00fe447..609caabf 100644
--- a/tests/test_internals_database.py
+++ b/tests/test_internals_database.py
@@ -396,6 +396,12 @@ async def test_execute_write_block_false(db):
     assert "Mystery!" == rows.rows[0][0]
 
 
+@pytest.mark.asyncio
+async def test_execute_write_has_correctly_prepared_connection(db):
+    # The sleep() function is only available if ds._prepare_connection() was called
+    await db.execute_write("select sleep(0.01)", block=True)
+
+
 @pytest.mark.asyncio
 async def test_execute_write_fn_block_false(db):
     def write_fn(conn):