diff --git a/pkg/skaffold/build/tag/git_commit.go b/pkg/skaffold/build/tag/git_commit.go
index 5a0553e1e36..bace4336057 100644
--- a/pkg/skaffold/build/tag/git_commit.go
+++ b/pkg/skaffold/build/tag/git_commit.go
@@ -21,8 +21,6 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"fmt"
-	"io"
-	"os"
 	"os/exec"
 	"path/filepath"
 	"sort"
@@ -152,7 +150,8 @@ func commitOrTag(currentTag string, tags []string, opts *Options) string {
 	return fmt.Sprintf("%s:%s", opts.ImageName, currentTag)
 }
 
-// The file state is dirty. To generate a unique suffix, let's hash all the modified files.
+// The file state is dirty. To generate a unique suffix, let's hash the diffs
+// of all modified files.
 // We add a -dirty-unique-id suffix to work well with local iterations.
 func dirtyTag(root string, opts *Options, currentTag string, lines []string) (string, error) {
 	h := sha256.New()
@@ -162,25 +161,23 @@ func dirtyTag(root string, opts *Options, currentTag string, lines []string) (st
 		}
 
 		if _, err := h.Write([]byte(statusLine)); err != nil {
-			return "", errors.Wrap(err, "adding deleted file to diff")
+			return "", errors.Wrap(err, "adding status line to hash")
 		}
 
+		// If the file has been deleted, there's no diff to generate.
 		if strings.HasPrefix(statusLine, "D") {
 			continue
 		}
 
-		changedPath := strings.Trim(statusLine[2:], " ")
-		f, err := os.Open(filepath.Join(root, changedPath))
+		changedPath := filepath.Join(root, strings.Trim(statusLine[2:], " "))
+		diff, err := runGit(root, "diff", changedPath)
 		if err != nil {
 			return "", errors.Wrap(err, "reading diff")
 		}
 
-		if _, err := io.Copy(h, f); err != nil {
-			f.Close()
-			return "", errors.Wrap(err, "reading diff")
+		if _, err := h.Write([]byte(diff)); err != nil {
+			return "", errors.Wrap(err, "adding diff to hash")
 		}
-
-		f.Close()
 	}
 
 	sha := h.Sum(nil)
diff --git a/pkg/skaffold/build/tag/git_commit_test.go b/pkg/skaffold/build/tag/git_commit_test.go
index fd9fa4f6767..713d59ef6e9 100644
--- a/pkg/skaffold/build/tag/git_commit_test.go
+++ b/pkg/skaffold/build/tag/git_commit_test.go
@@ -80,7 +80,7 @@ func TestGitCommit_GenerateFullyQualifiedImageName(t *testing.T) {
 			opts: &Options{
 				ImageName: "test",
 			},
-			expectedName: "test:eefe1b9-dirty-af8de1fde8be4367",
+			expectedName: "test:eefe1b9-dirty-8b8c4dad90faa822",
 			createGitRepo: func(dir string) {
 				gitInit(t, dir).
 					write("source.go", []byte("code")).
@@ -95,7 +95,7 @@ func TestGitCommit_GenerateFullyQualifiedImageName(t *testing.T) {
 				ImageName: "test",
 				Digest:    "sha256:12345abcde",
 			},
-			expectedName: "test:eefe1b9-dirty-af8de1fde8be4367",
+			expectedName: "test:eefe1b9-dirty-8b8c4dad90faa822",
 			createGitRepo: func(dir string) {
 				gitInit(t, dir).
 					write("source.go", []byte("code")).
@@ -110,7 +110,7 @@ func TestGitCommit_GenerateFullyQualifiedImageName(t *testing.T) {
 			opts: &Options{
 				ImageName: "test",
 			},
-			expectedName: "test:eefe1b9-dirty-bfe9b4566c9d3fec",
+			expectedName: "test:eefe1b9-dirty-e0bc2923501f63b7",
 			createGitRepo: func(dir string) {
 				gitInit(t, dir).
 					write("source.go", []byte("code")).
@@ -154,7 +154,7 @@ func TestGitCommit_GenerateFullyQualifiedImageName(t *testing.T) {
 			opts: &Options{
 				ImageName: "test",
 			},
-			expectedName: "test:eefe1b9-dirty-9c858d88cc0bf792",
+			expectedName: "test:eefe1b9-dirty-c9417af5dc664b60",
 			createGitRepo: func(dir string) {
 				gitInit(t, dir).
 					write("source.go", []byte("code")).
@@ -168,7 +168,7 @@ func TestGitCommit_GenerateFullyQualifiedImageName(t *testing.T) {
 			opts: &Options{
 				ImageName: "test",
 			},
-			expectedName: "test:eefe1b9-dirty-6534adc17ccd1cf4", // Must be <> each time a new name is used
+			expectedName: "test:eefe1b9-dirty-91fd2028ff0a5cf3", // Must be <> each time a new name is used
 			createGitRepo: func(dir string) {
 				gitInit(t, dir).
 					write("source.go", []byte("code")).
@@ -195,7 +195,7 @@ func TestGitCommit_GenerateFullyQualifiedImageName(t *testing.T) {
 			opts: &Options{
 				ImageName: "test",
 			},
-			expectedName: "test:a7b32a6-dirty-83715cdc64e43ee9",
+			expectedName: "test:a7b32a6-dirty-2dfb095d0f4830ad",
 			createGitRepo: func(dir string) {
 				gitInit(t, dir).
 					mkdir("sub/sub").