diff --git a/types/config.go b/types/config.go
index dba8714a..1c552e36 100644
--- a/types/config.go
+++ b/types/config.go
@@ -97,7 +97,7 @@ type Config struct {
 		Endpoint     string           `yaml:"endpoint" envconfig:"BEACONAPI_ENDPOINT"`
 		Endpoints    []EndpointConfig `yaml:"endpoints"`
 		EndpointsURL string           `yaml:"endpointsUrl" envconfig:"BEACONAPI_ENDPOINTS_URL"`
-		ClientIndex  int              `yaml:"clientIndex" envconfig:"BEACONAPI_CLIENT_INDEX"`
+		ClientIndex  *int             `yaml:"clientIndex" envconfig:"BEACONAPI_CLIENT_INDEX"`
 
 		LocalCacheSize       int    `yaml:"localCacheSize" envconfig:"BEACONAPI_LOCAL_CACHE_SIZE"`
 		SkipFinalAssignments bool   `yaml:"skipFinalAssignments" envconfig:"BEACONAPI_SKIP_FINAL_ASSIGNMENTS"`
diff --git a/utils/config.go b/utils/config.go
index e8396e8c..31e1ddd3 100644
--- a/utils/config.go
+++ b/utils/config.go
@@ -46,9 +46,9 @@ func ReadConfig(cfg *types.Config, path string) error {
 		}
 	}
 
-	// ClientIndex selects a specific endpoint by index (0-based)
-	if cfg.BeaconApi.ClientIndex >= 0 && cfg.BeaconApi.ClientIndex < len(cfg.BeaconApi.Endpoints) {
-		selectedEndpoint := cfg.BeaconApi.Endpoints[cfg.BeaconApi.ClientIndex]
+	// ClientIndex selects a specific endpoint by index (0-based), when explicitly set
+	if cfg.BeaconApi.ClientIndex != nil && *cfg.BeaconApi.ClientIndex >= 0 && *cfg.BeaconApi.ClientIndex < len(cfg.BeaconApi.Endpoints) {
+		selectedEndpoint := cfg.BeaconApi.Endpoints[*cfg.BeaconApi.ClientIndex]
 		cfg.BeaconApi.Endpoints = []types.EndpointConfig{selectedEndpoint}
 	}