diff --git a/command/container/prune.go b/command/container/prune.go
index 7088038614..be67fe4ca9 100644
--- a/command/container/prune.go
+++ b/command/container/prune.go
@@ -67,7 +67,7 @@ func runPrune(dockerCli *command.DockerCli, opts pruneOptions) (spaceReclaimed u
 	return
 }
 
-// RunPrune call the Container Prune API
+// RunPrune calls the Container Prune API
 // This returns the amount of space reclaimed and a detailed output string
 func RunPrune(dockerCli *command.DockerCli) (uint64, string, error) {
 	return runPrune(dockerCli, pruneOptions{force: true})
diff --git a/command/image/prune.go b/command/image/prune.go
index e5ad573130..46bd56cb10 100644
--- a/command/image/prune.go
+++ b/command/image/prune.go
@@ -83,7 +83,7 @@ func runPrune(dockerCli *command.DockerCli, opts pruneOptions) (spaceReclaimed u
 	return
 }
 
-// RunPrune call the Image Prune API
+// RunPrune calls the Image Prune API
 // This returns the amount of space reclaimed and a detailed output string
 func RunPrune(dockerCli *command.DockerCli, all bool) (uint64, string, error) {
 	return runPrune(dockerCli, pruneOptions{force: true, all: all})
diff --git a/command/prune/prune.go b/command/prune/prune.go
index 0b1374eda9..fd04c590b6 100644
--- a/command/prune/prune.go
+++ b/command/prune/prune.go
@@ -8,32 +8,32 @@ import (
 	"github.com/spf13/cobra"
 )
 
-// NewContainerPruneCommand return a cobra prune command for containers
+// NewContainerPruneCommand returns a cobra prune command for containers
 func NewContainerPruneCommand(dockerCli *command.DockerCli) *cobra.Command {
 	return container.NewPruneCommand(dockerCli)
 }
 
-// NewVolumePruneCommand return a cobra prune command for volumes
+// NewVolumePruneCommand returns a cobra prune command for volumes
 func NewVolumePruneCommand(dockerCli *command.DockerCli) *cobra.Command {
 	return volume.NewPruneCommand(dockerCli)
 }
 
-// NewImagePruneCommand return a cobra prune command for images
+// NewImagePruneCommand returns a cobra prune command for images
 func NewImagePruneCommand(dockerCli *command.DockerCli) *cobra.Command {
 	return image.NewPruneCommand(dockerCli)
 }
 
-// RunContainerPrune execute a prune command for containers
+// RunContainerPrune executes a prune command for containers
 func RunContainerPrune(dockerCli *command.DockerCli) (uint64, string, error) {
 	return container.RunPrune(dockerCli)
 }
 
-// RunVolumePrune execute a prune command for volumes
+// RunVolumePrune executes a prune command for volumes
 func RunVolumePrune(dockerCli *command.DockerCli) (uint64, string, error) {
 	return volume.RunPrune(dockerCli)
 }
 
-// RunImagePrune execute a prune command for images
+// RunImagePrune executes a prune command for images
 func RunImagePrune(dockerCli *command.DockerCli, all bool) (uint64, string, error) {
 	return image.RunPrune(dockerCli, all)
 }
diff --git a/command/system/df.go b/command/system/df.go
index 085d680fe8..293946c188 100644
--- a/command/system/df.go
+++ b/command/system/df.go
@@ -19,7 +19,7 @@ func NewDiskUsageCommand(dockerCli *command.DockerCli) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "df [OPTIONS]",
 		Short: "Show docker disk usage",
-		Args:  cli.RequiresMaxArgs(1),
+		Args:  cli.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runDiskUsage(dockerCli, opts)
 		},
diff --git a/command/system/prune.go b/command/system/prune.go
index 6a36fdd890..ea8a41380f 100644
--- a/command/system/prune.go
+++ b/command/system/prune.go
@@ -15,13 +15,13 @@ type pruneOptions struct {
 	all   bool
 }
 
-// NewPruneCommand creates a new cobra.Command for `docker du`
+// NewPruneCommand creates a new cobra.Command for `docker prune`
 func NewPruneCommand(dockerCli *command.DockerCli) *cobra.Command {
 	var opts pruneOptions
 
 	cmd := &cobra.Command{
 		Use:   "prune [OPTIONS]",
-		Short: "Remove unused data.",
+		Short: "Remove unused data",
 		Args:  cli.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runPrune(dockerCli, opts)
diff --git a/command/volume/prune.go b/command/volume/prune.go
index dc2d3e25bc..a4bb0092d6 100644
--- a/command/volume/prune.go
+++ b/command/volume/prune.go
@@ -67,7 +67,7 @@ func runPrune(dockerCli *command.DockerCli, opts pruneOptions) (spaceReclaimed u
 	return
 }
 
-// RunPrune call the Volume Prune API
+// RunPrune calls the Volume Prune API
 // This returns the amount of space reclaimed and a detailed output string
 func RunPrune(dockerCli *command.DockerCli) (uint64, string, error) {
 	return runPrune(dockerCli, pruneOptions{force: true})