@@ -22,9 +22,9 @@ import (

 )

 var (

-	// ErrPruneRunning is returned when a prune request is received while

+	// errPruneRunning is returned when a prune request is received while

 	// one is in progress

-	ErrPruneRunning = fmt.Errorf("a prune operation is already running")

+	errPruneRunning = fmt.Errorf("a prune operation is already running")

 	containersAcceptedFilters = map[string]bool{

 		"label":  true,

@@ -51,7 +51,7 @@ var (

 // ContainersPrune removes unused containers

 func (daemon *Daemon) ContainersPrune(ctx context.Context, pruneFilters filters.Args) (*types.ContainersPruneReport, error) {

 	if !atomic.CompareAndSwapInt32(&daemon.pruneRunning, 0, 1) {

-		return nil, ErrPruneRunning

+		return nil, errPruneRunning

 	}

 	defer atomic.StoreInt32(&daemon.pruneRunning, 0)

@@ -104,7 +104,7 @@ func (daemon *Daemon) ContainersPrune(ctx context.Context, pruneFilters filters.

 // VolumesPrune removes unused local volumes

 func (daemon *Daemon) VolumesPrune(ctx context.Context, pruneFilters filters.Args) (*types.VolumesPruneReport, error) {

 	if !atomic.CompareAndSwapInt32(&daemon.pruneRunning, 0, 1) {

-		return nil, ErrPruneRunning

+		return nil, errPruneRunning

 	}

 	defer atomic.StoreInt32(&daemon.pruneRunning, 0)

@@ -158,7 +158,7 @@ func (daemon *Daemon) VolumesPrune(ctx context.Context, pruneFilters filters.Arg

 // ImagesPrune removes unused images

 func (daemon *Daemon) ImagesPrune(ctx context.Context, pruneFilters filters.Args) (*types.ImagesPruneReport, error) {

 	if !atomic.CompareAndSwapInt32(&daemon.pruneRunning, 0, 1) {

-		return nil, ErrPruneRunning

+		return nil, errPruneRunning

 	}

 	defer atomic.StoreInt32(&daemon.pruneRunning, 0)

@@ -392,7 +392,7 @@ func (daemon *Daemon) clusterNetworksPrune(ctx context.Context, pruneFilters fil

 // NetworksPrune removes unused networks

 func (daemon *Daemon) NetworksPrune(ctx context.Context, pruneFilters filters.Args) (*types.NetworksPruneReport, error) {

 	if !atomic.CompareAndSwapInt32(&daemon.pruneRunning, 0, 1) {

-		return nil, ErrPruneRunning

+		return nil, errPruneRunning

 	}

 	defer atomic.StoreInt32(&daemon.pruneRunning, 0)