diff --git a/src/html/template/transition.go b/src/html/template/transition.go
index b486fcd2854..d2e028741a1 100644
--- a/src/html/template/transition.go
+++ b/src/html/template/transition.go
@@ -183,24 +183,54 @@ func tHTMLCmt(c context, s []byte) (context, int) {
 
 // specialTagEndMarkers maps element types to the character sequence that
 // case-insensitively signals the end of the special tag body.
-var specialTagEndMarkers = [...]string{
-	elementScript:   "</script",
-	elementStyle:    "</style",
-	elementTextarea: "</textarea",
-	elementTitle:    "</title",
+var specialTagEndMarkers = [...][]byte{
+	elementScript:   []byte("script"),
+	elementStyle:    []byte("style"),
+	elementTextarea: []byte("textarea"),
+	elementTitle:    []byte("title"),
 }
 
+var (
+	specialTagEndPrefix = []byte("</")
+	tagEndSeparators    = []byte("> \t\n\f/")
+)
+
 // tSpecialTagEnd is the context transition function for raw text and RCDATA
 // element states.
 func tSpecialTagEnd(c context, s []byte) (context, int) {
 	if c.element != elementNone {
-		if i := strings.Index(strings.ToLower(string(s)), specialTagEndMarkers[c.element]); i != -1 {
+		if i := indexTagEnd(s, specialTagEndMarkers[c.element]); i != -1 {
 			return context{}, i
 		}
 	}
 	return c, len(s)
 }
 
+// indexTagEnd finds the index of a special tag end in a case insensitive way, or returns -1
+func indexTagEnd(s []byte, tag []byte) int {
+	res := 0
+	plen := len(specialTagEndPrefix)
+	for len(s) > 0 {
+		// Try to find the tag end prefix first
+		i := bytes.Index(s, specialTagEndPrefix)
+		if i == -1 {
+			return i
+		}
+		s = s[i+plen:]
+		// Try to match the actual tag if there is still space for it
+		if len(tag) <= len(s) && bytes.EqualFold(tag, s[:len(tag)]) {
+			s = s[len(tag):]
+			// Check the tag is followed by a proper separator
+			if len(s) > 0 && bytes.IndexByte(tagEndSeparators, s[0]) != -1 {
+				return res + i
+			}
+			res += len(tag)
+		}
+		res += i + plen
+	}
+	return -1
+}
+
 // tAttr is the context transition function for the attribute state.
 func tAttr(c context, s []byte) (context, int) {
 	return c, len(s)
diff --git a/src/html/template/transition_test.go b/src/html/template/transition_test.go
new file mode 100644
index 00000000000..412a4c71b75
--- /dev/null
+++ b/src/html/template/transition_test.go
@@ -0,0 +1,60 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestFindEndTag(t *testing.T) {
+	tests := []struct {
+		s, tag string
+		want   int
+	}{
+		{"", "tag", -1},
+		{"hello </textarea> hello", "textarea", 6},
+		{"hello </TEXTarea> hello", "textarea", 6},
+		{"hello </textAREA>", "textarea", 6},
+		{"hello </textarea", "textareax", -1},
+		{"hello </textarea>", "tag", -1},
+		{"hello tag </textarea", "tag", -1},
+		{"hello </tag> </other> </textarea> <other>", "textarea", 22},
+		{"</textarea> <other>", "textarea", 0},
+		{"<div> </div> </TEXTAREA>", "textarea", 13},
+		{"<div> </div> </TEXTAREA\t>", "textarea", 13},
+		{"<div> </div> </TEXTAREA >", "textarea", 13},
+		{"<div> </div> </TEXTAREAfoo", "textarea", -1},
+		{"</TEXTAREAfoo </textarea>", "textarea", 14},
+		{"<</script >", "script", 1},
+		{"</script>", "textarea", -1},
+	}
+	for _, test := range tests {
+		if got := indexTagEnd([]byte(test.s), []byte(test.tag)); test.want != got {
+			t.Errorf("%q/%q: want\n\t%d\nbut got\n\t%d", test.s, test.tag, test.want, got)
+		}
+	}
+}
+
+func BenchmarkTemplateSpecialTags(b *testing.B) {
+
+	r := struct {
+		Name, Gift string
+	}{"Aunt Mildred", "bone china tea set"}
+
+	h1 := "<textarea> Hello Hello Hello </textarea> "
+	h2 := "<textarea> <p> Dear {{.Name}},\n{{with .Gift}}Thank you for the lovely {{.}}. {{end}}\nBest wishes. </p>\n</textarea>"
+	html := strings.Repeat(h1, 100) + h2 + strings.Repeat(h1, 100) + h2
+
+	var buf bytes.Buffer
+	for i := 0; i < b.N; i++ {
+		tmpl := Must(New("foo").Parse(html))
+		if err := tmpl.Execute(&buf, r); err != nil {
+			b.Fatal(err)
+		}
+		buf.Reset()
+	}
+}