diff --git a/cmd/gomtree/main.go b/cmd/gomtree/main.go
index cd81344..92c6f6a 100644
--- a/cmd/gomtree/main.go
+++ b/cmd/gomtree/main.go
@@ -396,7 +396,11 @@ func isTarSpec(spec *mtree.DirectoryHierarchy) bool {
 }
 
 func splitKeywordsArg(str string) []string {
-	return strings.Fields(strings.Replace(str, ",", " ", -1))
+	keywords := []string{}
+	for _, kw := range strings.Fields(strings.Replace(str, ",", " ", -1)) {
+		keywords = append(keywords, mtree.KeywordSynonym(kw))
+	}
+	return keywords
 }
 
 func inSlice(a string, list []string) bool {
diff --git a/hierarchy.go b/hierarchy.go
index 88a007d..3c8da39 100644
--- a/hierarchy.go
+++ b/hierarchy.go
@@ -38,7 +38,7 @@ func (dh DirectoryHierarchy) UsedKeywords() []string {
 				for _, kv := range kvs {
 					kw := KeyVal(kv).Keyword()
 					if !inSlice(kw, usedkeywords) {
-						usedkeywords = append(usedkeywords, kw)
+						usedkeywords = append(usedkeywords, KeywordSynonym(kw))
 					}
 				}
 			}
diff --git a/hierarchy_test.go b/hierarchy_test.go
new file mode 100644
index 0000000..0a58e56
--- /dev/null
+++ b/hierarchy_test.go
@@ -0,0 +1,38 @@
+package mtree
+
+import (
+	"strings"
+	"testing"
+)
+
+var checklist = []struct {
+	blob string
+	set  []string
+}{
+	{blob: `
+#       machine: bananaboat
+#          tree: .git
+#          date: Wed Nov 16 14:54:17 2016
+
+# .
+/set type=file nlink=1 mode=0664 uid=1000 gid=100
+. size=4096 type=dir mode=0755 nlink=8 time=1479326055.423853146
+  .COMMIT_EDITMSG.un~ size=1006 mode=0644 time=1479325423.450468662 sha1digest=dead0face
+  .TAG_EDITMSG.un~ size=1069 mode=0600 time=1471362316.801317529 sha256digest=dead0face
+`, set: []string{"size", "mode", "time", "sha256digest"}},
+}
+
+func TestUsedKeywords(t *testing.T) {
+	for i, item := range checklist {
+		dh, err := ParseSpec(strings.NewReader(item.blob))
+		if err != nil {
+			t.Error(err)
+		}
+		used := dh.UsedKeywords()
+		for _, k := range item.set {
+			if !inSlice(k, used) {
+				t.Errorf("%d: expected to find %q in %q", i, k, used)
+			}
+		}
+	}
+}
diff --git a/keywords.go b/keywords.go
index fd996d3..93916f4 100644
--- a/keywords.go
+++ b/keywords.go
@@ -251,6 +251,31 @@ var (
 	}
 )
 
+// KeywordSynonym returns the canonical name for keywords that have synonyms,
+// and just returns the name provided if there is no synonym. In this way it
+// ought to be safe to wrap any keyword name.
+func KeywordSynonym(name string) string {
+	switch name {
+	case "md5":
+		return "md5digest"
+	case "rmd160":
+		return "ripemd160digest"
+	case "rmd160digest":
+		return "ripemd160digest"
+	case "sha1":
+		return "sha1digest"
+	case "sha256":
+		return "sha256digest"
+	case "sha384":
+		return "sha384digest"
+	case "sha512":
+		return "sha512digest"
+	case "xattrs":
+		return "xattr"
+	}
+	return name
+}
+
 var (
 	modeKeywordFunc = func(path string, info os.FileInfo, r io.Reader) (string, error) {
 		permissions := info.Mode().Perm()
@@ -292,7 +317,7 @@ var (
 			if _, err := io.Copy(h, r); err != nil {
 				return "", err
 			}
-			return fmt.Sprintf("%s=%x", name, h.Sum(nil)), nil
+			return fmt.Sprintf("%s=%x", KeywordSynonym(name), h.Sum(nil)), nil
 		}
 	}
 	tartimeKeywordFunc = func(path string, info os.FileInfo, r io.Reader) (string, error) {
diff --git a/keywords_test.go b/keywords_test.go
index 5860fc0..4411453 100644
--- a/keywords_test.go
+++ b/keywords_test.go
@@ -93,3 +93,33 @@ func TestKeywordsTimeTar(t *testing.T) {
 		}
 	}
 }
+
+func TestKeywordSynonym(t *testing.T) {
+	checklist := []struct {
+		give, expect string
+	}{
+		{give: "time", expect: "time"},
+		{give: "md5", expect: "md5digest"},
+		{give: "md5digest", expect: "md5digest"},
+		{give: "rmd160", expect: "ripemd160digest"},
+		{give: "rmd160digest", expect: "ripemd160digest"},
+		{give: "ripemd160digest", expect: "ripemd160digest"},
+		{give: "sha1", expect: "sha1digest"},
+		{give: "sha1digest", expect: "sha1digest"},
+		{give: "sha256", expect: "sha256digest"},
+		{give: "sha256digest", expect: "sha256digest"},
+		{give: "sha384", expect: "sha384digest"},
+		{give: "sha384digest", expect: "sha384digest"},
+		{give: "sha512", expect: "sha512digest"},
+		{give: "sha512digest", expect: "sha512digest"},
+		{give: "xattr", expect: "xattr"},
+		{give: "xattrs", expect: "xattr"},
+	}
+
+	for i, check := range checklist {
+		got := KeywordSynonym(check.give)
+		if got != check.expect {
+			t.Errorf("%d: expected %q; got %q", i, check.expect, got)
+		}
+	}
+}
diff --git a/test/cli/0004.sh b/test/cli/0004.sh
new file mode 100644
index 0000000..b538285
--- /dev/null
+++ b/test/cli/0004.sh
@@ -0,0 +1,24 @@
+#!/bin/bash
+set -e
+#set -x
+
+name=$(basename $0)
+root=$1
+gomtree=$(readlink -f ${root}/gomtree)
+t=$(mktemp -d /tmp/go-mtree.XXXXXX)
+
+echo "[${name}] Running in ${t}"
+
+pushd ${root}
+git archive --format=tar HEAD^{tree} . > ${t}/${name}.tar
+mkdir -p ${t}/extract
+tar -C ${t}/extract/ -xf ${t}/${name}.tar
+
+## This is a checking that keyword synonyms are respected
+${gomtree} -k sha1digest -c -p ${t}/extract/ > ${t}/${name}.mtree
+${gomtree} -k sha1 -f ${t}/${name}.mtree -p ${t}/extract/
+${gomtree} -k sha1 -c -p ${t}/extract/ > ${t}/${name}.mtree
+${gomtree} -k sha1digest -f ${t}/${name}.mtree -p ${t}/extract/
+
+popd
+rm -rf ${t}