diff --git a/simple_server_main.cc b/simple_server_main.cc
index c008513..225859a 100644
--- a/simple_server_main.cc
+++ b/simple_server_main.cc
@@ -26,7 +26,7 @@
 
 // root_private_key is an Ed25519 private key used by simple_server. The
 // private part consists of all zeros and so is only for use in this example.
-constexpr uint8_t root_private_key[ED25519_PRIVATE_KEY_LEN] = {
+constexpr uint8_t root_private_key[roughtime::kPrivateKeyLength] = {
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3b, 0x6a, 0x27, 0xbc,