2 files changed, 13 insertions, 6 deletions
diff --git a/src/encoding/xml/xml.go b/src/encoding/xml/xml.go
index c902f1295a..c14954df15 100644
--- a/src/encoding/xml/xml.go
+++ b/src/encoding/xml/xml.go
@@ -768,6 +768,12 @@ func (d *Decoder) rawToken() (Token, error) {
 					}
 					b0, b1 = b1, b
 				}
+
+				// Replace the comment with a space in the returned Directive
+				// body, so that markup parts that were separated by the comment
+				// (like a "<" and a "!") don't get joined when re-encoding the
+				// Directive, taking new semantic meaning.
+				d.buf.WriteByte(' ')
 			}
 		}
 		return Directive(d.buf.Bytes()), nil
diff --git a/src/encoding/xml/xml_test.go b/src/encoding/xml/xml_test.go
index 47d0c39167..19152dbdb6 100644
--- a/src/encoding/xml/xml_test.go
+++ b/src/encoding/xml/xml_test.go
@@ -802,11 +802,11 @@ var directivesWithCommentsInput = `
 
 var directivesWithCommentsTokens = []Token{
 	CharData("\n"),
-	Directive(`DOCTYPE [<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]`),
+	Directive(`DOCTYPE [ <!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]`),
 	CharData("\n"),
-	Directive(`DOCTYPE [<!ENTITY go "Golang">]`),
+	Directive(`DOCTYPE [<!ENTITY go "Golang"> ]`),
 	CharData("\n"),
-	Directive(`DOCTYPE <!-> <!>    [<!ENTITY go "Golang">]`),
+	Directive(`DOCTYPE <!-> <!>       [<!ENTITY go "Golang"> ]`),
 	CharData("\n"),
 }
 
@@ -1051,9 +1051,10 @@ func testRoundTrip(t *testing.T, input string) {
 
 func TestRoundTrip(t *testing.T) {
 	tests := map[string]string{
-		"leading colon":  `<::Test ::foo="bar"><:::Hello></:::Hello><Hello></Hello></::Test>`,
-		"trailing colon": `<foo abc:="x"></foo>`,
-		"double colon":   `<x:y:foo></x:y:foo>`,
+		"leading colon":          `<::Test ::foo="bar"><:::Hello></:::Hello><Hello></Hello></::Test>`,
+		"trailing colon":         `<foo abc:="x"></foo>`,
+		"double colon":           `<x:y:foo></x:y:foo>`,
+		"comments in directives": `<!ENTITY x<!<!-- c1 [ " -->--x --> > <e></e> <!DOCTYPE xxx [ x<!-- c2 " -->--x ]>`,
 	}
 	for name, input := range tests {
 		t.Run(name, func(t *testing.T) { testRoundTrip(t, input) })