--- a/services/common/blocklist-clients.js
+++ b/services/common/blocklist-clients.js
@@ -219,17 +219,17 @@ class BlocklistClient {
 
       // If there is no data currently in the collection, attempt to import
       // initial data from the application defaults.
       // This allows to avoid synchronizing the whole collection content on
       // cold start.
       if (!collectionLastModified && loadDump) {
         try {
           const initialData = await this.loadDumpFile();
-          await collection.db.loadDump(initialData.data);
+          await collection.loadDump(initialData.data);
           collectionLastModified = await collection.db.getLastModified();
         } catch (e) {
           // Report but go-on.
           Cu.reportError(e);
         }
       }
 
       // If the data is up to date, there's no need to sync. We still need
@@ -237,17 +237,19 @@ class BlocklistClient {
       if (lastModified <= collectionLastModified) {
         this.updateLastCheck(serverTime);
         reportStatus = UptakeTelemetry.STATUS.UP_TO_DATE;
         return;
       }
 
       // Fetch changes from server.
       try {
-        const {ok} = await collection.sync({remote});
+        // Server changes have priority during synchronization.
+        const strategy = Kinto.syncStrategy.SERVER_WINS;
+        const {ok} = await collection.sync({remote, strategy});
         if (!ok) {
           // Some synchronization conflicts occured.
           reportStatus = UptakeTelemetry.STATUS.CONFLICT_ERROR;
           throw new Error("Sync failed");
         }
       } catch (e) {
         if (e.message == INVALID_SIGNATURE) {
           // Signature verification failed during synchronzation.

--- a/services/common/tests/unit/test_blocklist_clients.js
+++ b/services/common/tests/unit/test_blocklist_clients.js
@@ -109,32 +109,63 @@ function run_test() {
 
   run_next_test();
 
   do_register_cleanup(function() {
     server.stop(() => { });
   });
 }
 
+add_task(async function test_initial_dump_is_loaded_as_synced_when_collection_is_empty() {
+  for (let {client} of gBlocklistClients) {
+    // Test an empty db populates, but don't reach server (specified timestamp <= dump).
+    await client.maybeSync(1, Date.now());
+
+    // Open the collection, verify the loaded data has status to synced:
+    const sqliteHandle = await FirefoxAdapter.openConnection({path: kintoFilename});
+    const collection = kintoCollection(client.collectionName, sqliteHandle);
+    const list = await collection.list();
+    equal(list.data[0]._status, "synced");
+    await sqliteHandle.close();
+  }
+});
+add_task(clear_state);
+
 add_task(async function test_records_obtained_from_server_are_stored_in_db() {
   for (let {client} of gBlocklistClients) {
     // Test an empty db populates
     await client.maybeSync(2000, Date.now(), {loadDump: false});
 
     // Open the collection, verify it's been populated:
     // Our test data has a single record; it should be in the local collection
     const sqliteHandle = await FirefoxAdapter.openConnection({path: kintoFilename});
     let collection = kintoCollection(client.collectionName, sqliteHandle);
     let list = await collection.list();
     equal(list.data.length, 1);
     await sqliteHandle.close();
   }
 });
 add_task(clear_state);
 
+add_task(async function test_records_changes_are_overwritten_by_server_changes() {
+  const {client} = gBlocklistClients[0];
+
+  // Create some local conflicting data, and make sure it syncs without error.
+  const sqliteHandle = await FirefoxAdapter.openConnection({path: kintoFilename});
+  const collection = kintoCollection(client.collectionName, sqliteHandle);
+  await collection.create({
+    "versionRange": [],
+    "id": "9d500963-d80e-3a91-6e74-66f3811b99cc"
+  }, { useRecordId: true });
+  await sqliteHandle.close();
+
+  await client.maybeSync(2000, Date.now(), {loadDump: false});
+});
+add_task(clear_state);
+
 add_task(async function test_list_is_written_to_file_in_profile() {
   for (let {client, testData} of gBlocklistClients) {
     const filePath = OS.Path.join(OS.Constants.Path.profileDir, client.filename);
     const profFile = new FileUtils.File(filePath);
     strictEqual(profFile.exists(), false);
 
     await client.maybeSync(2000, Date.now(), {loadDump: false});