diff --git a/js/js.go b/js/js.go
index 40fad480a..05681041d 100644
--- a/js/js.go
+++ b/js/js.go
@@ -863,13 +863,13 @@ func (m *jsMinifier) minifyExpr(i js.IExpr, prec js.OpPrec) {
 			expr = expr.Link
 		}
 		data := expr.Data
-		if bytes.Equal(data, undefinedBytes) { // TODO: only if not defined
+		if expr.Decl == js.NoDecl && bytes.Equal(data, undefinedBytes) {
 			if js.OpMember < prec {
 				m.write(groupedZeroIndexBytes)
 			} else {
 				m.write(zeroIndexBytes)
 			}
-		} else if bytes.Equal(data, infinityBytes) { // TODO: only if not defined
+		} else if expr.Decl == js.NoDecl && bytes.Equal(data, infinityBytes) {
 			if js.OpMul < prec {
 				m.write(groupedOneDivZeroBytes)
 			} else {
diff --git a/js/js_test.go b/js/js_test.go
index 4106f3497..d3bc051b3 100644
--- a/js/js_test.go
+++ b/js/js_test.go
@@ -190,11 +190,11 @@ func TestJS(t *testing.T) {
 		{`x=undefined`, `x=0[0]`},
 		{`x=undefined()`, `x=0[0]()`},
 		{`x=undefined.a`, `x=0[0].a`},
-		//{`{const undefined=5;x=undefined}`, `{const undefined=5;x=undefined}`},
+		{`{const undefined=5;x=undefined}`, `{const undefined=5;x=undefined}`},
 		{`x=Infinity`, `x=1/0`},
 		{`x=Infinity()`, `x=(1/0)()`},
 		{`x=2**Infinity`, `x=2**(1/0)`},
-		//{`{const Infinity=5;x=Infinity}`, `{const Infinity=5;x=Infinity}`},
+		{`{const Infinity=5;x=Infinity}`, `{const Infinity=5;x=Infinity}`},
 		{`!""`, `!0`},
 		{`!"foobar"`, `!1`},
 		{`class a extends undefined {}`, `class a extends 0[0]{}`},