diff --git a/pkg/upstream/container/exec.go b/pkg/upstream/container/exec.go
index 686f8944..82a2c570 100644
--- a/pkg/upstream/container/exec.go
+++ b/pkg/upstream/container/exec.go
@@ -13,6 +13,8 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+// RunExec runs a command on a remote container. io.Writer corresponds to the
+// command output.
 func RunExec(dockerCli command.Cli, client *apiclient.Client, containerID string,
 	execConfig *types.ExecConfig) (io.Writer, error) {
 	ctx := context.Background()