diff --git a/mmv.go b/mmv.go
index d5fc829..42dfbae 100644
--- a/mmv.go
+++ b/mmv.go
@@ -13,8 +13,16 @@ func Rename(files map[string]string) error {
 	if err != nil {
 		return err
 	}
-	for _, r := range rs {
+	for i, r := range rs {
 		if err := doRename(r.src, r.dst); err != nil {
+			// undo on error not to leave the temporary files
+			// this does not undo directory creation
+			for i--; i >= 0; i-- {
+				if r = rs[i]; os.Rename(r.dst, r.src) != nil {
+					// something wrong happens so give up not to overwrite files
+					break
+				}
+			}
 			return err
 		}
 	}
diff --git a/mmv_test.go b/mmv_test.go
index 862e659..b41e300 100644
--- a/mmv_test.go
+++ b/mmv_test.go
@@ -254,6 +254,30 @@ func TestRename(t *testing.T) {
 			},
 			err: "duplicate destination: foo",
 		},
+		{
+			name: "undo on error",
+			files: map[string]string{
+				"foo":  "bar",
+				"bar":  "foo",
+				"baz":  "qux",
+				"qux":  "quux",
+				"quux": "baz",
+			},
+			count: 7,
+			contents: map[string]string{
+				"foo": "0",
+				"bar": "1",
+				"baz": "2",
+				"qux": "3",
+			},
+			expected: map[string]string{
+				"foo": "0",
+				"bar": "1",
+				"baz": "2",
+				"qux": "3",
+			},
+			err: "quux: ", // no such file or directory
+		},
 		{
 			name: "create destination directory",
 			files: map[string]string{