diff --git a/html/doctype.go b/html/doctype.go
index c484e5a94..bca3ae9a0 100644
--- a/html/doctype.go
+++ b/html/doctype.go
@@ -87,7 +87,7 @@ func parseDoctype(s string) (n *Node, quirks bool) {
 			}
 		}
 		if lastAttr := n.Attr[len(n.Attr)-1]; lastAttr.Key == "system" &&
-			strings.ToLower(lastAttr.Val) == "http://www.ibm.com/data/dtd/v11/ibmxhtml1-transitional.dtd" {
+			strings.EqualFold(lastAttr.Val, "http://www.ibm.com/data/dtd/v11/ibmxhtml1-transitional.dtd") {
 			quirks = true
 		}
 	}
diff --git a/html/foreign.go b/html/foreign.go
index 9da9e9dc4..e8515d8e8 100644
--- a/html/foreign.go
+++ b/html/foreign.go
@@ -40,8 +40,7 @@ func htmlIntegrationPoint(n *Node) bool {
 		if n.Data == "annotation-xml" {
 			for _, a := range n.Attr {
 				if a.Key == "encoding" {
-					val := strings.ToLower(a.Val)
-					if val == "text/html" || val == "application/xhtml+xml" {
+					if strings.EqualFold(a.Val, "text/html") || strings.EqualFold(a.Val, "application/xhtml+xml") {
 						return true
 					}
 				}
diff --git a/html/parse.go b/html/parse.go
index d67705d9e..643c674e3 100644
--- a/html/parse.go
+++ b/html/parse.go
@@ -1035,7 +1035,7 @@ func inBodyIM(p *parser) bool {
 			if p.tok.DataAtom == a.Input {
 				for _, t := range p.tok.Attr {
 					if t.Key == "type" {
-						if strings.ToLower(t.Val) == "hidden" {
+						if strings.EqualFold(t.Val, "hidden") {
 							// Skip setting framesetOK = false
 							return true
 						}
@@ -1463,7 +1463,7 @@ func inTableIM(p *parser) bool {
 			return inHeadIM(p)
 		case a.Input:
 			for _, t := range p.tok.Attr {
-				if t.Key == "type" && strings.ToLower(t.Val) == "hidden" {
+				if t.Key == "type" && strings.EqualFold(t.Val, "hidden") {
 					p.addElement()
 					p.oe.pop()
 					return true