diff --git a/cmd/copy.go b/cmd/copy.go
index 8a6cce1..203646b 100644
--- a/cmd/copy.go
+++ b/cmd/copy.go
@@ -135,7 +135,7 @@ func setOptions(c *cli.Context, supervisor *copier.Supervisor) error {
 		supervisor.ExecTimeout = timeout
 	}
 
-	if r := c.Int("retries"); r > 0 {
+	if r := c.Int("retries"); r >= 0 {
 		supervisor.Retries = r
 	}
 
diff --git a/exec.go b/exec.go
index e07edf6..ac085f9 100644
--- a/exec.go
+++ b/exec.go
@@ -2,6 +2,7 @@ package copier
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"os"
 
@@ -11,9 +12,12 @@ import (
 
 // An Exec copies files at a given ratelimit.
 type Exec struct {
+	opened bool
 	size   int64
 	ctx    context.Context
-	reader *ProxyReader
+	r      io.ReadCloser  // input file
+	w      io.WriteCloser // output file
+	pr     *ProxyReader
 	From   string
 	To     string
 	Speed  float64
@@ -62,26 +66,29 @@ func (e *Exec) Execute() error {
 		e.status = StatusCopied
 	}
 
-	r, err := os.Open(e.From)
+	e.opened = true
+
+	e.r, err = os.Open(e.From)
 	if err != nil {
 		return errors.Annotate(err, "source")
 	}
-	defer r.Close()
+	defer e.r.Close()
 
 	w, err := os.Create(e.To)
 	if err != nil {
 		return errors.Annotate(err, "destination")
 	}
 	defer w.Close()
+	e.w = w
 
-	rr := shapeio.NewReaderWithContext(r, e.ctx)
+	rr := shapeio.NewReaderWithContext(e.r, e.ctx)
 	rr.SetRateLimit(e.Speed)
 
-	e.reader = NewProxyReader(rr) // Used for progressbar
-	defer e.reader.Close()
+	e.pr = NewProxyReader(rr) // Used for progressbar
+	defer e.pr.Close()
 	e.Ready <- struct{}{}
 
-	if _, err = io.Copy(w, e.reader); err != nil {
+	if _, err = io.Copy(e.w, e.pr); err != nil {
 		return errors.Annotate(err, "copy")
 	}
 
@@ -105,5 +112,23 @@ func (e *Exec) Size() int64 {
 
 // Reader returns the file reader.
 func (e *Exec) Reader() *ProxyReader {
-	return e.reader
+	return e.pr
+}
+
+// ForceClose force closes all its IO objects.
+func (e *Exec) ForceClose() {
+	if !e.opened {
+		return
+	}
+
+	e.asyncClose(e.pr)
+	e.asyncClose(e.r)
+	e.asyncClose(e.w)
+	fmt.Println("Forced close.")
+}
+
+func (e *Exec) asyncClose(c io.Closer) {
+	if c != nil {
+		go c.Close()
+	}
 }
diff --git a/supervisor.go b/supervisor.go
index 7f214c5..4c57834 100644
--- a/supervisor.go
+++ b/supervisor.go
@@ -92,18 +92,17 @@ func (s *Supervisor) Execute() error {
 	return nil
 }
 
-func (s *Supervisor) execute(from, to string, retries int, err2 error) error {
-	if retries == 0 {
+func (s *Supervisor) execute(from, to string, retries int, err2 error) (err error) {
+	if retries < 0 {
 		return err2 // keep last error
 	}
 
 	errc := make(chan error)
-	var err error
 
 	ctx, cancel := context.WithTimeout(s.Context, s.ExecTimeout)
 	defer cancel()
 
-	cp := NewExecWithContext(ctx, from, to, s.Speed)
+	cp := NewExec(from, to, s.Speed)
 	cp.Speed = s.Speed
 	go func() {
 		if err = cp.Execute(); err != nil {
@@ -126,6 +125,7 @@ func (s *Supervisor) execute(from, to string, retries int, err2 error) error {
 			ready = true
 		case <-ctx.Done():
 			if ctx.Err() != nil {
+				cp.ForceClose()
 				time.Sleep(s.RetryInterval)
 				err = s.execute(from, to, retries-1, ctx.Err())
 			}
@@ -133,6 +133,7 @@ func (s *Supervisor) execute(from, to string, retries int, err2 error) error {
 			terminated = true
 		case err = <-errc:
 			if err != nil {
+				cp.ForceClose()
 				time.Sleep(s.RetryInterval)
 				err = s.execute(from, to, retries-1, err)
 			}
diff --git a/utils.go b/utils.go
index 177aa13..5582cbe 100644
--- a/utils.go
+++ b/utils.go
@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 )
 
 const (
@@ -135,8 +136,10 @@ func MoreRecent(dst, src string) (bool, error) {
 
 // A ProxyReader is proxified reader.
 type ProxyReader struct {
+	m      sync.Mutex
 	reader io.Reader
 	writer io.Writer
+	closed bool
 	c      chan int
 }
 
@@ -151,19 +154,39 @@ func NewProxyReader(r io.Reader) *ProxyReader {
 // Read implements io.Reader
 func (r *ProxyReader) Read(b []byte) (n int, err error) {
 	n, err = r.reader.Read(b)
-	r.c <- n
+
+	if !r.Closed() {
+		r.c <- n
+	}
 	return
 }
 
 // Close the reader when it implements io.Closer
 func (r *ProxyReader) Close() (err error) {
-	if closer, ok := r.reader.(io.Closer); ok {
-		return closer.Close()
+	if r.Closed() {
+		return nil
+	}
+
+	if r.reader != nil {
+		if closer, ok := r.reader.(io.Closer); ok {
+			return closer.Close()
+		}
 	}
 	close(r.c)
+
+	r.m.Lock()
+	defer r.m.Unlock()
+	r.closed = true
 	return
 }
 
+// Closed returns the reader status.
+func (r *ProxyReader) Closed() bool {
+	r.m.Lock()
+	defer r.m.Unlock()
+	return r.closed
+}
+
 // ReadChunk returns the number of read bytes for a chunk.
 func (r *ProxyReader) ReadChunk() <-chan int {
 	return r.c