diff --git a/les/odr_test.go b/les/odr_test.go
index 97217e9488..74808b345f 100644
--- a/les/odr_test.go
+++ b/les/odr_test.go
@@ -188,6 +188,12 @@ func testOdr(t *testing.T, protocol int, expFail uint64, checkCached bool, fn od
 
 	client.handler.synchronise(client.peer.peer)
 
+	// Ensure the client has synced all necessary data.
+	clientHead := client.handler.backend.blockchain.CurrentHeader()
+	if clientHead.Number.Uint64() != 4 {
+		t.Fatalf("Failed to sync the chain with server, head: %v", clientHead.Number.Uint64())
+	}
+
 	test := func(expFail uint64) {
 		// Mark this as a helper to put the failures at the correct lines
 		t.Helper()
diff --git a/les/request_test.go b/les/request_test.go
index 69b57ca317..8d09703c57 100644
--- a/les/request_test.go
+++ b/les/request_test.go
@@ -81,8 +81,15 @@ func testAccess(t *testing.T, protocol int, fn accessTestFn) {
 	// Assemble the test environment
 	server, client, tearDown := newClientServerEnv(t, 4, protocol, nil, nil, 0, false, true)
 	defer tearDown()
+
 	client.handler.synchronise(client.peer.peer)
 
+	// Ensure the client has synced all necessary data.
+	clientHead := client.handler.backend.blockchain.CurrentHeader()
+	if clientHead.Number.Uint64() != 4 {
+		t.Fatalf("Failed to sync the chain with server, head: %v", clientHead.Number.Uint64())
+	}
+
 	test := func(expFail uint64) {
 		for i := uint64(0); i <= server.handler.blockchain.CurrentHeader().Number.Uint64(); i++ {
 			bhash := rawdb.ReadCanonicalHash(server.db, i)
diff --git a/les/test_helper.go b/les/test_helper.go
index 7b4b0521f8..67b0225fed 100644
--- a/les/test_helper.go
+++ b/les/test_helper.go
@@ -517,7 +517,7 @@ func newClientServerEnv(t *testing.T, blocks int, protocol int, callback indexer
 	if connect {
 		cpeer, err1, speer, err2 = newTestPeerPair("peer", protocol, server, client)
 		select {
-		case <-time.After(time.Millisecond * 100):
+		case <-time.After(time.Millisecond * 300):
 		case err := <-err1:
 			t.Fatalf("peer 1 handshake error: %v", err)
 		case err := <-err2: