diff --git a/CHANGELOG.md b/CHANGELOG.md
index b4ed6efb01e..9410c779151 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,18 @@
 # Changelog
 
+## Unreleased
+
+* Fix U+30FB and U+FF65 in identifier names in ES5 vs. ES6+ ([#1599](https://github.com/evanw/esbuild/issues/1599))
+
+    The ES6 specification caused two code points that were previously valid in identifier names in ES5 to no longer be valid in identifier names in ES6+. The two code points are:
+
+    * `U+30FB` i.e. `KATAKANA MIDDLE DOT` i.e. `・`
+    * `U+FF65` i.e. `HALFWIDTH KATAKANA MIDDLE DOT` i.e. `･`
+
+    This means that using ES6+ parsing rules will fail to parse some valid ES5 code, and generating valid ES5 code may fail to be parsed using ES6+ parsing rules. For example, esbuild would previously fail to parse `x.y･` even though it's valid ES5 code (since it's not valid ES6+ code) and esbuild could generate `{y･:x}` when minifying even though it's not valid ES6+ code (since it's valid ES5 code). This problem is the result of my incorrect assumption that ES6 is a superset of ES5.
+
+    As of this release, esbuild will now parse a superset of ES5 and ES6+ and will now quote identifier names when possible if it's not considered to be a valid identifier name in either ES5 or ES6+. In other words, a union of ES5 and ES6 rules is used for parsing and the intersection of ES5 and ES6 rules is used for printing.
+
 ## 0.12.27
 
 * Update JavaScript syntax feature compatibility tables ([#1594](https://github.com/evanw/esbuild/issues/1594))
diff --git a/internal/js_lexer/js_lexer.go b/internal/js_lexer/js_lexer.go
index ed161e26aab..27aa6a4e83c 100644
--- a/internal/js_lexer/js_lexer.go
+++ b/internal/js_lexer/js_lexer.go
@@ -577,17 +577,17 @@ func IsIdentifier(text string) bool {
 	return true
 }
 
-func IsIdentifierES5(text string) bool {
+func IsIdentifierES5AndESNext(text string) bool {
 	if len(text) == 0 {
 		return false
 	}
 	for i, codePoint := range text {
 		if i == 0 {
-			if !IsIdentifierStartES5(codePoint) {
+			if !IsIdentifierStartES5AndESNext(codePoint) {
 				return false
 			}
 		} else {
-			if !IsIdentifierContinueES5(codePoint) {
+			if !IsIdentifierContinueES5AndESNext(codePoint) {
 				return false
 			}
 		}
@@ -652,8 +652,8 @@ func IsIdentifierUTF16(text []uint16) bool {
 	return true
 }
 
-// This does "IsIdentifierES5(UTF16ToString(text))" without any allocations
-func IsIdentifierES5UTF16(text []uint16) bool {
+// This does "IsIdentifierES5AndESNext(UTF16ToString(text))" without any allocations
+func IsIdentifierES5AndESNextUTF16(text []uint16) bool {
 	n := len(text)
 	if n == 0 {
 		return false
@@ -668,11 +668,11 @@ func IsIdentifierES5UTF16(text []uint16) bool {
 			}
 		}
 		if isStart {
-			if !IsIdentifierStartES5(r1) {
+			if !IsIdentifierStartES5AndESNext(r1) {
 				return false
 			}
 		} else {
-			if !IsIdentifierContinueES5(r1) {
+			if !IsIdentifierContinueES5AndESNext(r1) {
 				return false
 			}
 		}
@@ -695,7 +695,7 @@ func IsIdentifierStart(codePoint rune) bool {
 		return false
 	}
 
-	return unicode.Is(idStart, codePoint)
+	return unicode.Is(idStartES5OrESNext, codePoint)
 }
 
 func IsIdentifierContinue(codePoint rune) bool {
@@ -718,10 +718,10 @@ func IsIdentifierContinue(codePoint rune) bool {
 		return true
 	}
 
-	return unicode.Is(idContinue, codePoint)
+	return unicode.Is(idContinueES5OrESNext, codePoint)
 }
 
-func IsIdentifierStartES5(codePoint rune) bool {
+func IsIdentifierStartES5AndESNext(codePoint rune) bool {
 	switch codePoint {
 	case '_', '$',
 		'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
@@ -736,10 +736,10 @@ func IsIdentifierStartES5(codePoint rune) bool {
 		return false
 	}
 
-	return unicode.Is(idStartES5, codePoint)
+	return unicode.Is(idStartES5AndESNext, codePoint)
 }
 
-func IsIdentifierContinueES5(codePoint rune) bool {
+func IsIdentifierContinueES5AndESNext(codePoint rune) bool {
 	switch codePoint {
 	case '_', '$', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
 		'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
@@ -759,7 +759,7 @@ func IsIdentifierContinueES5(codePoint rune) bool {
 		return true
 	}
 
-	return unicode.Is(idContinueES5, codePoint)
+	return unicode.Is(idContinueES5AndESNext, codePoint)
 }
 
 // See the "White Space Code Points" table in the ECMAScript standard
diff --git a/internal/js_lexer/unicode.go b/internal/js_lexer/unicode.go
index 6dbb0900515..c20cd543542 100644
--- a/internal/js_lexer/unicode.go
+++ b/internal/js_lexer/unicode.go
@@ -3,7 +3,7 @@ package js_lexer
 
 import "unicode"
 
-var idStartES5 = &unicode.RangeTable{
+var idStartES5AndESNext = &unicode.RangeTable{
 	LatinOffset: 117,
 	R16: []unicode.Range16{
 		{Lo: 0x41, Hi: 0x5a, Stride: 1},
@@ -266,7 +266,7 @@ var idStartES5 = &unicode.RangeTable{
 	},
 }
 
-var idContinueES5 = &unicode.RangeTable{
+var idContinueES5AndESNext = &unicode.RangeTable{
 	LatinOffset: 128,
 	R16: []unicode.Range16{
 		{Lo: 0x30, Hi: 0x39, Stride: 1},
@@ -578,7 +578,8 @@ var idContinueES5 = &unicode.RangeTable{
 		{Lo: 0x3041, Hi: 0x3094, Stride: 1},
 		{Lo: 0x3099, Hi: 0x309a, Stride: 1},
 		{Lo: 0x309d, Hi: 0x309e, Stride: 1},
-		{Lo: 0x30a1, Hi: 0x30fe, Stride: 1},
+		{Lo: 0x30a1, Hi: 0x30fa, Stride: 1},
+		{Lo: 0x30fc, Hi: 0x30fe, Stride: 1},
 		{Lo: 0x3105, Hi: 0x312c, Stride: 1},
 		{Lo: 0x3131, Hi: 0x318e, Stride: 1},
 		{Lo: 0x31a0, Hi: 0x31b7, Stride: 1},
@@ -610,7 +611,7 @@ var idContinueES5 = &unicode.RangeTable{
 		{Lo: 0xff21, Hi: 0xff3a, Stride: 1},
 		{Lo: 0xff3f, Hi: 0xff3f, Stride: 1},
 		{Lo: 0xff41, Hi: 0xff5a, Stride: 1},
-		{Lo: 0xff65, Hi: 0xffbe, Stride: 1},
+		{Lo: 0xff66, Hi: 0xffbe, Stride: 1},
 		{Lo: 0xffc2, Hi: 0xffc7, Stride: 1},
 		{Lo: 0xffca, Hi: 0xffcf, Stride: 1},
 		{Lo: 0xffd2, Hi: 0xffd7, Stride: 1},
@@ -618,7 +619,7 @@ var idContinueES5 = &unicode.RangeTable{
 	},
 }
 
-var idStart = &unicode.RangeTable{
+var idStartES5OrESNext = &unicode.RangeTable{
 	LatinOffset: 117,
 	R16: []unicode.Range16{
 		{Lo: 0x41, Hi: 0x5a, Stride: 1},
@@ -1248,7 +1249,7 @@ var idStart = &unicode.RangeTable{
 	},
 }
 
-var idContinue = &unicode.RangeTable{
+var idContinueES5OrESNext = &unicode.RangeTable{
 	LatinOffset: 129,
 	R16: []unicode.Range16{
 		{Lo: 0x30, Hi: 0x39, Stride: 1},
@@ -1600,8 +1601,7 @@ var idContinue = &unicode.RangeTable{
 		{Lo: 0x3038, Hi: 0x303c, Stride: 1},
 		{Lo: 0x3041, Hi: 0x3096, Stride: 1},
 		{Lo: 0x3099, Hi: 0x309f, Stride: 1},
-		{Lo: 0x30a1, Hi: 0x30fa, Stride: 1},
-		{Lo: 0x30fc, Hi: 0x30ff, Stride: 1},
+		{Lo: 0x30a1, Hi: 0x30ff, Stride: 1},
 		{Lo: 0x3105, Hi: 0x312f, Stride: 1},
 		{Lo: 0x3131, Hi: 0x318e, Stride: 1},
 		{Lo: 0x31a0, Hi: 0x31bf, Stride: 1},
@@ -1678,7 +1678,7 @@ var idContinue = &unicode.RangeTable{
 		{Lo: 0xff21, Hi: 0xff3a, Stride: 1},
 		{Lo: 0xff3f, Hi: 0xff3f, Stride: 1},
 		{Lo: 0xff41, Hi: 0xff5a, Stride: 1},
-		{Lo: 0xff66, Hi: 0xffbe, Stride: 1},
+		{Lo: 0xff65, Hi: 0xffbe, Stride: 1},
 		{Lo: 0xffc2, Hi: 0xffc7, Stride: 1},
 		{Lo: 0xffca, Hi: 0xffcf, Stride: 1},
 		{Lo: 0xffd2, Hi: 0xffd7, Stride: 1},
diff --git a/internal/js_parser/js_parser_test.go b/internal/js_parser/js_parser_test.go
index d0b73518be7..5f06ace7994 100644
--- a/internal/js_parser/js_parser_test.go
+++ b/internal/js_parser/js_parser_test.go
@@ -574,6 +574,20 @@ func TestRegExp(t *testing.T) {
 `)
 }
 
+func TestUnicodeIdentifierNames(t *testing.T) {
+	// There are two code points that are valid in identifiers in ES5 but not in ES6+:
+	//
+	//   U+30FB KATAKANA MIDDLE DOT
+	//   U+FF65 HALFWIDTH KATAKANA MIDDLE DOT
+	//
+	expectPrinted(t, "x = {x・: 0}", "x = { \"x・\": 0 };\n")
+	expectPrinted(t, "x = {x･: 0}", "x = { \"x･\": 0 };\n")
+	expectPrinted(t, "x = {xπ: 0}", "x = { xπ: 0 };\n")
+	expectPrinted(t, "x = y.x・", "x = y[\"x・\"];\n")
+	expectPrinted(t, "x = y.x･", "x = y[\"x･\"];\n")
+	expectPrinted(t, "x = y.xπ", "x = y.xπ;\n")
+}
+
 func TestIdentifierEscapes(t *testing.T) {
 	expectPrinted(t, "var _\\u0076\\u0061\\u0072", "var _var;\n")
 	expectParseError(t, "var \\u0076\\u0061\\u0072", "<stdin>: error: Expected identifier but found \"\\\\u0076\\\\u0061\\\\u0072\"\n")
diff --git a/internal/js_printer/js_printer.go b/internal/js_printer/js_printer.go
index 052eb543768..c8f3dedda68 100644
--- a/internal/js_printer/js_printer.go
+++ b/internal/js_printer/js_printer.go
@@ -510,19 +510,19 @@ func (p *printer) printClauseAlias(alias string) {
 // JavaScript language target that we support.
 
 func CanEscapeIdentifier(name string, unsupportedJSFeatures compat.JSFeature, asciiOnly bool) bool {
-	return js_lexer.IsIdentifierES5(name) && (!asciiOnly ||
+	return js_lexer.IsIdentifierES5AndESNext(name) && (!asciiOnly ||
 		!unsupportedJSFeatures.Has(compat.UnicodeEscapes) ||
 		!js_lexer.ContainsNonBMPCodePoint(name))
 }
 
 func (p *printer) canPrintIdentifier(name string) bool {
-	return js_lexer.IsIdentifierES5(name) && (!p.options.ASCIIOnly ||
+	return js_lexer.IsIdentifierES5AndESNext(name) && (!p.options.ASCIIOnly ||
 		!p.options.UnsupportedFeatures.Has(compat.UnicodeEscapes) ||
 		!js_lexer.ContainsNonBMPCodePoint(name))
 }
 
 func (p *printer) canPrintIdentifierUTF16(name []uint16) bool {
-	return js_lexer.IsIdentifierES5UTF16(name) && (!p.options.ASCIIOnly ||
+	return js_lexer.IsIdentifierES5AndESNextUTF16(name) && (!p.options.ASCIIOnly ||
 		!p.options.UnsupportedFeatures.Has(compat.UnicodeEscapes) ||
 		!js_lexer.ContainsNonBMPCodePointUTF16(name))
 }
diff --git a/scripts/gen-unicode-table.js b/scripts/gen-unicode-table.js
index cc3ee65483a..481ae2eeab1 100644
--- a/scripts/gen-unicode-table.js
+++ b/scripts/gen-unicode-table.js
@@ -45,10 +45,20 @@ const idContinueES5 = idStartES5.concat(
 // is presumed to be the Unicode set, collection 10646.
 //
 // UnicodeIDStart: any Unicode code point with the Unicode property “ID_Start”
-const idStart = require('@unicode/unicode-13.0.0/Binary_Property/ID_Start/code-points');
+const idStartESNext = require('@unicode/unicode-13.0.0/Binary_Property/ID_Start/code-points');
+const idStartESNextSet = new Set(idStartESNext);
 
 // UnicodeIDContinue: any Unicode code point with the Unicode property “ID_Continue”
-const idContinue = require('@unicode/unicode-13.0.0/Binary_Property/ID_Continue/code-points');
+const idContinueESNext = require('@unicode/unicode-13.0.0/Binary_Property/ID_Continue/code-points');
+const idContinueESNextSet = new Set(idContinueESNext);
+
+// These identifiers are valid in both ES5 and ES6+ (i.e. an intersection of both)
+const idStartES5AndESNext = idStartES5.filter(n => idStartESNextSet.has(n));
+const idContinueES5AndESNext = idContinueES5.filter(n => idContinueESNextSet.has(n));
+
+// These identifiers are valid in either ES5 or ES6+ (i.e. a union of both)
+const idStartES5OrESNext = [...new Set(idStartES5.concat(idStartESNext))].sort((a, b) => a - b);
+const idContinueES5OrESNext = [...new Set(idContinueES5.concat(idContinueESNext))].sort((a, b) => a - b);
 
 function generateRangeTable(codePoints) {
   let lines = [];
@@ -105,11 +115,11 @@ package js_lexer
 
 import "unicode"
 
-var idStartES5 = ${generateRangeTable(idStartES5)}
+var idStartES5AndESNext = ${generateRangeTable(idStartES5AndESNext)}
 
-var idContinueES5 = ${generateRangeTable(idContinueES5)}
+var idContinueES5AndESNext = ${generateRangeTable(idContinueES5AndESNext)}
 
-var idStart = ${generateRangeTable(idStart)}
+var idStartES5OrESNext = ${generateRangeTable(idStartES5OrESNext)}
 
-var idContinue = ${generateRangeTable(idContinue)}
+var idContinueES5OrESNext = ${generateRangeTable(idContinueES5OrESNext)}
 `);