diff --git a/setup/config/config.go b/setup/config/config.go
index df5e44585..836e1d66e 100644
--- a/setup/config/config.go
+++ b/setup/config/config.go
@@ -234,7 +234,7 @@ func loadConfig(
 	for _, key := range c.Global.OldVerifyKeys {
 		switch {
 		case key.KeyID == "":
-			return nil, fmt.Errorf("key ID must be specified for old_verify_keys")
+			return nil, fmt.Errorf("key ID must be specified if public_key is specified")
 
 		case len(key.PublicKey) == ed25519.PublicKeySize:
 			continue
diff --git a/setup/config/config_global.go b/setup/config/config_global.go
index 17fff741f..2efae0d5a 100644
--- a/setup/config/config_global.go
+++ b/setup/config/config_global.go
@@ -131,7 +131,7 @@ type OldVerifyKeys struct {
 	PublicKey gomatrixserverlib.Base64Bytes `yaml:"public_key"`
 
 	// The key ID of the private key.
-	KeyID gomatrixserverlib.KeyID `yaml:"-"`
+	KeyID gomatrixserverlib.KeyID `yaml:"key_id"`
 
 	// When the private key was designed as "expired", as a UNIX timestamp
 	// in millisecond precision.