diff --git a/Dockerfile b/Dockerfile
index 3fea9ab6d..0f0a83700 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -14,11 +14,11 @@
 #   docker run --rm -v $PWD:/home/travis/restic restic/test gb test -v ./backend
 #
 # build the image for an older version of Go:
-#   docker build --build-arg GOVERSION=1.3.3 -t restic/test:go1.3.3 .
+#   docker build --build-arg GOVERSION=1.6.4 -t restic/test:go1.6.4 .
 
 FROM ubuntu:14.04
 
-ARG GOVERSION=1.7
+ARG GOVERSION=1.7.5
 ARG GOARCH=amd64
 
 # install dependencies
diff --git a/src/restic/backend/rest/rest.go b/src/restic/backend/rest/rest.go
index 7121de945..2c133872b 100644
--- a/src/restic/backend/rest/rest.go
+++ b/src/restic/backend/rest/rest.go
@@ -17,7 +17,7 @@ import (
 	"restic/backend"
 )
 
-const connLimit = 10
+const connLimit = 40
 
 // make sure the rest backend implements restic.Backend
 var _ restic.Backend = &restBackend{}
diff --git a/src/restic/backend/s3/s3.go b/src/restic/backend/s3/s3.go
index 054c715e0..c7b92c80a 100644
--- a/src/restic/backend/s3/s3.go
+++ b/src/restic/backend/s3/s3.go
@@ -3,6 +3,7 @@ package s3
 import (
 	"bytes"
 	"io"
+	"net/http"
 	"path"
 	"restic"
 	"strings"
@@ -15,7 +16,7 @@ import (
 	"restic/debug"
 )
 
-const connLimit = 10
+const connLimit = 40
 
 // s3 is a backend which stores the data on an S3 endpoint.
 type s3 struct {
@@ -36,6 +37,10 @@ func Open(cfg Config) (restic.Backend, error) {
 	}
 
 	be := &s3{client: client, bucketname: cfg.Bucket, prefix: cfg.Prefix}
+
+	tr := &http.Transport{MaxIdleConnsPerHost: connLimit}
+	client.SetCustomTransport(tr)
+
 	be.createConnections()
 
 	found, err := client.BucketExists(cfg.Bucket)
@@ -104,6 +109,18 @@ func (be *s3) Save(h restic.Handle, rd io.Reader) (err error) {
 	return errors.Wrap(err, "client.PutObject")
 }
 
+// wrapReader wraps an io.ReadCloser to run an additional function on Close.
+type wrapReader struct {
+	io.ReadCloser
+	f func()
+}
+
+func (wr wrapReader) Close() error {
+	err := wr.ReadCloser.Close()
+	wr.f()
+	return err
+}
+
 // Load returns a reader that yields the contents of the file at h at the
 // given offset. If length is nonzero, only a portion of the file is
 // returned. rd must be closed after use.
@@ -125,29 +142,49 @@ func (be *s3) Load(h restic.Handle, length int, offset int64) (io.ReadCloser, er
 
 	objName := be.s3path(h)
 
+	// get token for connection
 	<-be.connChan
-	defer func() {
-		be.connChan <- struct{}{}
-	}()
 
 	obj, err := be.client.GetObject(be.bucketname, objName)
 	if err != nil {
 		debug.Log("  err %v", err)
+
+		// return token
+		be.connChan <- struct{}{}
+
 		return nil, errors.Wrap(err, "client.GetObject")
 	}
 
 	// if we're going to read the whole object, just pass it on.
 	if length == 0 {
 		debug.Log("Load %v: pass on object", h)
+
 		_, err = obj.Seek(offset, 0)
 		if err != nil {
 			_ = obj.Close()
+
+			// return token
+			be.connChan <- struct{}{}
+
 			return nil, errors.Wrap(err, "obj.Seek")
 		}
 
-		return obj, nil
+		rd := wrapReader{
+			ReadCloser: obj,
+			f: func() {
+				debug.Log("Close()")
+				// return token
+				be.connChan <- struct{}{}
+			},
+		}
+		return rd, nil
 	}
 
+	defer func() {
+		// return token
+		be.connChan <- struct{}{}
+	}()
+
 	// otherwise use a buffer with ReadAt
 	info, err := obj.Stat()
 	if err != nil {
diff --git a/src/restic/backend/test/tests.go b/src/restic/backend/test/tests.go
index a6105f9e9..5c11d2e4b 100644
--- a/src/restic/backend/test/tests.go
+++ b/src/restic/backend/test/tests.go
@@ -245,21 +245,25 @@ func TestLoad(t testing.TB) {
 		buf, err := ioutil.ReadAll(rd)
 		if err != nil {
 			t.Errorf("Load(%d, %d) ReadAll() returned unexpected error: %v", l, o, err)
+			rd.Close()
 			continue
 		}
 
 		if l <= len(d) && len(buf) != l {
 			t.Errorf("Load(%d, %d) wrong number of bytes read: want %d, got %d", l, o, l, len(buf))
+			rd.Close()
 			continue
 		}
 
 		if l > len(d) && len(buf) != len(d) {
 			t.Errorf("Load(%d, %d) wrong number of bytes read for overlong read: want %d, got %d", l, o, l, len(buf))
+			rd.Close()
 			continue
 		}
 
 		if !bytes.Equal(buf, d) {
 			t.Errorf("Load(%d, %d) returned wrong bytes", l, o)
+			rd.Close()
 			continue
 		}