diff --git a/client.go b/client.go
index df2fd22..b1291a7 100644
--- a/client.go
+++ b/client.go
@@ -637,11 +637,13 @@ func (c *Client) Start() (addr net.Addr, err error) {
 	}
 
 	env := []string{
-		fmt.Sprintf("%s=%s", c.config.MagicCookieKey, c.config.MagicCookieValue),
 		fmt.Sprintf("PLUGIN_MIN_PORT=%d", c.config.MinPort),
 		fmt.Sprintf("PLUGIN_MAX_PORT=%d", c.config.MaxPort),
 		fmt.Sprintf("PLUGIN_PROTOCOL_VERSIONS=%s", strings.Join(versionStrings, ",")),
 	}
+	if len(c.config.MagicCookieKey) > 0 {
+		env = append(env, fmt.Sprintf("%s=%s", c.config.MagicCookieKey, c.config.MagicCookieValue))
+	}
 	if c.config.GRPCBrokerMultiplex {
 		env = append(env, fmt.Sprintf("%s=true", envMultiplexGRPC))
 	}