diff --git a/builder/tarsum.go b/builder/tarsum.go
index 201e3ef7d9..48372cb01c 100644
--- a/builder/tarsum.go
+++ b/builder/tarsum.go
@@ -138,7 +138,7 @@ func (c *tarSumContext) Walk(root string, walkFn WalkFunc) error {
 		}
 
 		sum := rel
-		if tsInfo := c.sums.GetFile(rel); tsInfo != nil {
+		if tsInfo := c.sums.GetFile(filepath.ToSlash(rel)); tsInfo != nil {
 			sum = tsInfo.Sum()
 		}
 		fi := &HashedFileInfo{PathFileInfo{FileInfo: info, FilePath: fullpath}, sum}
diff --git a/integration-cli/docker_api_build_test.go b/integration-cli/docker_api_build_test.go
index 49de71c9af..805ec74097 100644
--- a/integration-cli/docker_api_build_test.go
+++ b/integration-cli/docker_api_build_test.go
@@ -4,6 +4,8 @@ import (
 	"archive/tar"
 	"bytes"
 	"net/http"
+	"regexp"
+	"strings"
 
 	"github.com/docker/docker/pkg/integration/checker"
 	"github.com/go-check/check"
@@ -255,3 +257,60 @@ func (s *DockerSuite) TestBuildApiDockerfileSymlink(c *check.C) {
 	// a nonexistent file.
 	c.Assert(string(out), checker.Contains, "Cannot locate specified Dockerfile: Dockerfile", check.Commentf("Didn't complain about leaving build context"))
 }
+
+func (s *DockerSuite) TestBuildApiUnnormalizedTarPaths(c *check.C) {
+	// Make sure that build context tars with entries of the form
+	// x/./y don't cause caching false positives.
+
+	buildFromTarContext := func(fileContents []byte) string {
+		buffer := new(bytes.Buffer)
+		tw := tar.NewWriter(buffer)
+		defer tw.Close()
+
+		dockerfile := []byte(`FROM busybox
+	COPY dir /dir/`)
+		err := tw.WriteHeader(&tar.Header{
+			Name: "Dockerfile",
+			Size: int64(len(dockerfile)),
+		})
+		//failed to write tar file header
+		c.Assert(err, checker.IsNil)
+
+		_, err = tw.Write(dockerfile)
+		// failed to write Dockerfile in tar file content
+		c.Assert(err, checker.IsNil)
+
+		err = tw.WriteHeader(&tar.Header{
+			Name: "dir/./file",
+			Size: int64(len(fileContents)),
+		})
+		//failed to write tar file header
+		c.Assert(err, checker.IsNil)
+
+		_, err = tw.Write(fileContents)
+		// failed to write file contents in tar file content
+		c.Assert(err, checker.IsNil)
+
+		// failed to close tar archive
+		c.Assert(tw.Close(), checker.IsNil)
+
+		res, body, err := sockRequestRaw("POST", "/build", buffer, "application/x-tar")
+		c.Assert(err, checker.IsNil)
+		c.Assert(res.StatusCode, checker.Equals, http.StatusOK)
+
+		out, err := readBody(body)
+		c.Assert(err, checker.IsNil)
+		lines := strings.Split(string(out), "\n")
+		c.Assert(len(lines), checker.GreaterThan, 1)
+		c.Assert(lines[len(lines)-2], checker.Matches, ".*Successfully built [0-9a-f]{12}.*")
+
+		re := regexp.MustCompile("Successfully built ([0-9a-f]{12})")
+		matches := re.FindStringSubmatch(lines[len(lines)-2])
+		return matches[1]
+	}
+
+	imageA := buildFromTarContext([]byte("abc"))
+	imageB := buildFromTarContext([]byte("def"))
+
+	c.Assert(imageA, checker.Not(checker.Equals), imageB)
+}
diff --git a/pkg/tarsum/tarsum.go b/pkg/tarsum/tarsum.go
index 4dc89bd415..154788db82 100644
--- a/pkg/tarsum/tarsum.go
+++ b/pkg/tarsum/tarsum.go
@@ -28,6 +28,7 @@ import (
 	"fmt"
 	"hash"
 	"io"
+	"path"
 	"strings"
 )
 
@@ -235,7 +236,7 @@ func (ts *tarSum) Read(buf []byte) (int, error) {
 				}
 				return n, err
 			}
-			ts.currentFile = strings.TrimSuffix(strings.TrimPrefix(currentHeader.Name, "./"), "/")
+			ts.currentFile = path.Clean(currentHeader.Name)
 			if err := ts.encodeHeader(currentHeader); err != nil {
 				return 0, err
 			}