@@ -308,22 +308,20 @@ func calcCopyInfo(b *Builder, cmdName string, cInfos *[]*copyInfo, origPath stri

 			ci.destPath = ci.destPath + filename

 		}

-		// Calc the checksum, only if we're using the cache

-		if b.UtilizeCache {

-			r, err := archive.Tar(tmpFileName, archive.Uncompressed)

-			if err != nil {

-				return err

-			}

-			tarSum, err := tarsum.NewTarSum(r, true, tarsum.Version0)

-			if err != nil {

-				return err

-			}

-			if _, err := io.Copy(ioutil.Discard, tarSum); err != nil {

-				return err

-			}

-			ci.hash = tarSum.Sum(nil)

-			r.Close()

+		// Calc the checksum, even if we're using the cache

+		r, err := archive.Tar(tmpFileName, archive.Uncompressed)

+		if err != nil {

+			return err

 		}

+		tarSum, err := tarsum.NewTarSum(r, true, tarsum.Version0)

+		if err != nil {

+			return err

+		}

+		if _, err := io.Copy(ioutil.Discard, tarSum); err != nil {

+			return err

+		}

+		ci.hash = tarSum.Sum(nil)

+		r.Close()

 		return nil

 	}

@@ -358,12 +356,6 @@ func calcCopyInfo(b *Builder, cmdName string, cInfos *[]*copyInfo, origPath stri

 	ci.decompress = allowDecompression

 	*cInfos = append(*cInfos, &ci)

-	// If not using cache don't need to do anything else.

-	// If we are using a cache then calc the hash for the src file/dir

-	if !b.UtilizeCache {

-		return nil

-	}

-

 	// Deal with the single file case

 	if !fi.IsDir() {

 		// This will match first file in sums of the archive

@@ -2302,6 +2302,46 @@ func TestBuildWithoutCache(t *testing.T) {

 	logDone("build - without cache")

 }

+func TestBuildConditionalCache(t *testing.T) {

+	name := "testbuildconditionalcache"

+	name2 := "testbuildconditionalcache2"

+	defer deleteImages(name, name2)

+

+	dockerfile := `

+		FROM busybox

+        ADD foo /tmp/`

+	ctx, err := fakeContext(dockerfile, map[string]string{

+		"foo": "hello",

+	})

+

+	id1, err := buildImageFromContext(name, ctx, true)

+	if err != nil {

+		t.Fatalf("Error building #1: %s", err)

+	}

+

+	if err := ctx.Add("foo", "bye"); err != nil {

+		t.Fatalf("Error modifying foo: %s", err)

+	}

+

+	id2, err := buildImageFromContext(name, ctx, false)

+	if err != nil {

+		t.Fatalf("Error building #2: %s", err)

+	}

+	if id2 == id1 {

+		t.Fatal("Should not have used the cache")

+	}

+

+	id3, err := buildImageFromContext(name, ctx, true)

+	if err != nil {

+		t.Fatalf("Error building #3: %s", err)

+	}

+	if id3 != id2 {

+		t.Fatal("Should have used the cache")

+	}

+

+	logDone("build - conditional cache")

+}

+

 func TestBuildADDLocalFileWithCache(t *testing.T) {

 	name := "testbuildaddlocalfilewithcache"

 	name2 := "testbuildaddlocalfilewithcache2"