diff --git a/selfupdate/uncompress.go b/selfupdate/uncompress.go
new file mode 100644
index 0000000..9c3070d
--- /dev/null
+++ b/selfupdate/uncompress.go
@@ -0,0 +1,62 @@
+package selfupdate
+
+import (
+	"archive/tar"
+	"archive/zip"
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"strings"
+)
+
+func uncompress(src io.Reader, url, cmd string) (io.Reader, error) {
+	if strings.HasSuffix(url, ".zip") {
+		// Zip format requires its file size for uncompressing.
+		// So we need to read the HTTP response into a buffer at first.
+		buf, err := ioutil.ReadAll(src)
+		if err != nil {
+			return nil, err
+		}
+
+		r := bytes.NewReader(buf)
+		z, err := zip.NewReader(r, r.Size())
+		if err != nil {
+			return nil, err
+		}
+
+		for _, file := range z.File {
+			if file.Name == cmd {
+				return file.Open()
+			}
+		}
+
+		return nil, fmt.Errorf("File '%s' for the command is not found in %s", cmd, url)
+	} else if strings.HasSuffix(url, ".gzip") {
+		return gzip.NewReader(src)
+	} else if strings.HasSuffix(url, ".tar.gz") {
+		gz, err := gzip.NewReader(src)
+		if err != nil {
+			return nil, err
+		}
+
+		t := tar.NewReader(gz)
+		for {
+			h, err := t.Next()
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				return nil, err
+			}
+			if h.Name == cmd {
+				return t, nil
+			}
+		}
+
+		return nil, fmt.Errorf("File '%s' for the command is not found in %s", cmd, url)
+	}
+
+	return src, nil
+}
diff --git a/selfupdate/update.go b/selfupdate/update.go
index 89836b4..592822a 100644
--- a/selfupdate/update.go
+++ b/selfupdate/update.go
@@ -1,71 +1,14 @@
 package selfupdate
 
 import (
-	"archive/tar"
-	"archive/zip"
-	"bytes"
-	"compress/gzip"
 	"fmt"
 	"github.com/blang/semver"
 	"github.com/inconshreveable/go-update"
-	"io"
-	"io/ioutil"
 	"net/http"
 	"os"
 	"path/filepath"
-	"strings"
 )
 
-func uncompress(src io.Reader, url, cmd string) (io.Reader, error) {
-	if strings.HasSuffix(url, ".zip") {
-		// Zip format requires its file size for uncompressing.
-		// So we need to read the HTTP response into a buffer at first.
-		buf, err := ioutil.ReadAll(src)
-		if err != nil {
-			return nil, err
-		}
-
-		r := bytes.NewReader(buf)
-		z, err := zip.NewReader(r, r.Size())
-		if err != nil {
-			return nil, err
-		}
-
-		for _, file := range z.File {
-			if file.Name == cmd {
-				return file.Open()
-			}
-		}
-
-		return nil, fmt.Errorf("File '%s' for the command is not found in %s", cmd, url)
-	} else if strings.HasSuffix(url, ".gzip") {
-		return gzip.NewReader(src)
-	} else if strings.HasSuffix(url, ".tar.gz") {
-		gz, err := gzip.NewReader(src)
-		if err != nil {
-			return nil, err
-		}
-
-		t := tar.NewReader(gz)
-		for {
-			h, err := t.Next()
-			if err == io.EOF {
-				break
-			}
-			if err != nil {
-				return nil, err
-			}
-			if h.Name == cmd {
-				return t, nil
-			}
-		}
-
-		return nil, fmt.Errorf("File '%s' for the command is not found in %s", cmd, url)
-	}
-
-	return src, nil
-}
-
 // UpdateTo download an executable from assetURL and replace the current binary with the downloaded one. cmdPath is a file path to command executable.
 func UpdateTo(assetURL, cmdPath string) error {
 	res, err := http.Get(assetURL)