diff --git a/internal/config/config.go b/internal/config/config.go
index d815802..b8e041b 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -236,14 +236,12 @@ func New(_ fx.Lifecycle, params Params) (*Config, error) {
 // unparseable or invalid is an error: defaults apply only to omitted
 // keys, never to invalid explicit values.
 func newFromSmartConfig(sc *smartconfig.Config) (*Config, error) {
-	if sc != nil {
-		err := validateKnownKeys(sc)
-		if err != nil {
-			return nil, err
-		}
+	err := validateKnownKeys(sc)
+	if err != nil {
+		return nil, err
 	}
 
-	err := validateAllowlistHostsValue(sc)
+	err = validateAllowlistHostsValue(sc)
 	if err != nil {
 		return nil, err
 	}
@@ -337,8 +335,13 @@ func newFromSmartConfig(sc *smartconfig.Config) (*Config, error) {
 // being silently ignored, and rejects keys that are explicitly set to
 // null: a null is a SET value, never an omission, so it must not
 // silently take the default. The env section is permitted because
-// smartconfig consumes it for environment variable injection.
+// smartconfig consumes it for environment variable injection. A nil sc
+// means no config file, which has no keys to check.
 func validateKnownKeys(sc *smartconfig.Config) error {
+	if sc == nil {
+		return nil
+	}
+
 	var unknown, nullKeys []string
 
 	for key, value := range sc.Data() {