diff --git a/opts/swarmopts/config.go b/opts/swarmopts/config.go
index 78e8f886b6..4d98ed5257 100644
--- a/opts/swarmopts/config.go
+++ b/opts/swarmopts/config.go
@@ -86,7 +86,7 @@ func (*ConfigOpt) Type() string {
 
 // String returns a string repr of this option
 func (o *ConfigOpt) String() string {
-	configs := []string{}
+	configs := make([]string, 0, len(o.values))
 	for _, config := range o.values {
 		repr := fmt.Sprintf("%s -> %s", config.ConfigName, config.File.Name)
 		configs = append(configs, repr)
diff --git a/opts/swarmopts/secret.go b/opts/swarmopts/secret.go
index b28970af9a..834e8ae273 100644
--- a/opts/swarmopts/secret.go
+++ b/opts/swarmopts/secret.go
@@ -85,7 +85,7 @@ func (*SecretOpt) Type() string {
 
 // String returns a string repr of this option
 func (o *SecretOpt) String() string {
-	secrets := []string{}
+	secrets := make([]string, 0, len(o.values))
 	for _, secret := range o.values {
 		repr := fmt.Sprintf("%s -> %s", secret.SecretName, secret.File.Name)
 		secrets = append(secrets, repr)