diff --git a/api/go1.13.txt b/api/go1.13.txt
index 0f5e3eeefd..16f11cf2b7 100644
--- a/api/go1.13.txt
+++ b/api/go1.13.txt
@@ -8021,9 +8021,6 @@ pkg syscall (windows-amd64), type SysProcAttr struct, ThreadAttributes *Security
 pkg testing, func Init()
 pkg testing, method (*B) ReportMetric(float64, string)
 pkg testing, type BenchmarkResult struct, Extra map[string]float64
-pkg text/scanner, const AllowDigitSeparators = 1024
-pkg text/scanner, const AllowDigitSeparators ideal-int
-pkg text/scanner, const GoTokens = 2036
 pkg text/template, method (ExecError) Unwrap() error
 pkg time, method (Duration) Microseconds() int64
 pkg time, method (Duration) Milliseconds() int64
diff --git a/src/text/scanner/scanner.go b/src/text/scanner/scanner.go
index fa5a0cd70d..e0847a7239 100644
--- a/src/text/scanner/scanner.go
+++ b/src/text/scanner/scanner.go
@@ -58,17 +58,19 @@ func (pos Position) String() string {
 // For instance, if the mode is ScanIdents (not ScanStrings), the string
 // "foo" is scanned as the token sequence '"' Ident '"'.
 //
+// Use GoTokens to configure the Scanner such that it accepts all Go
+// literal tokens including Go identifiers. Comments will be skipped.
+//
 const (
-	ScanIdents           = 1 << -Ident
-	ScanInts             = 1 << -Int
-	ScanFloats           = 1 << -Float // includes Ints and hexadecimal floats
-	ScanChars            = 1 << -Char
-	ScanStrings          = 1 << -String
-	ScanRawStrings       = 1 << -RawString
-	ScanComments         = 1 << -Comment
-	SkipComments         = 1 << -skipComment          // if set with ScanComments, comments become white space
-	AllowDigitSeparators = 1 << -allowDigitSeparators // if set, number literals may contain underscores as digit separators
-	GoTokens             = ScanIdents | ScanFloats | ScanChars | ScanStrings | ScanRawStrings | ScanComments | SkipComments | AllowDigitSeparators
+	ScanIdents     = 1 << -Ident
+	ScanInts       = 1 << -Int
+	ScanFloats     = 1 << -Float // includes Ints and hexadecimal floats
+	ScanChars      = 1 << -Char
+	ScanStrings    = 1 << -String
+	ScanRawStrings = 1 << -RawString
+	ScanComments   = 1 << -Comment
+	SkipComments   = 1 << -skipComment // if set with ScanComments, comments become white space
+	GoTokens       = ScanIdents | ScanFloats | ScanChars | ScanStrings | ScanRawStrings | ScanComments | SkipComments
 )
 
 // The result of Scan is one of these tokens or a Unicode character.
@@ -84,7 +86,6 @@ const (
 
 	// internal use only
 	skipComment
-	allowDigitSeparators
 )
 
 var tokenString = map[rune]string{
@@ -363,8 +364,7 @@ func lower(ch rune) rune     { return ('a' - 'A') | ch } // returns lower-case c
 func isDecimal(ch rune) bool { return '0' <= ch && ch <= '9' }
 func isHex(ch rune) bool     { return '0' <= ch && ch <= '9' || 'a' <= lower(ch) && lower(ch) <= 'f' }
 
-// digits accepts the sequence { digit } (if AllowDigitSeparators is not set)
-// or { digit | '_' } (if AllowDigitSeparators is set), starting with ch0.
+// digits accepts the sequence { digit | '_' } starting with ch0.
 // If base <= 10, digits accepts any decimal digit but records
 // the first invalid digit >= base in *invalid if *invalid == 0.
 // digits returns the first rune that is not part of the sequence
@@ -374,7 +374,7 @@ func (s *Scanner) digits(ch0 rune, base int, invalid *rune) (ch rune, digsep int
 	ch = ch0
 	if base <= 10 {
 		max := rune('0' + base)
-		for isDecimal(ch) || ch == '_' && s.Mode&AllowDigitSeparators != 0 {
+		for isDecimal(ch) || ch == '_' {
 			ds := 1
 			if ch == '_' {
 				ds = 2
@@ -385,7 +385,7 @@ func (s *Scanner) digits(ch0 rune, base int, invalid *rune) (ch rune, digsep int
 			ch = s.next()
 		}
 	} else {
-		for isHex(ch) || ch == '_' && s.Mode&AllowDigitSeparators != 0 {
+		for isHex(ch) || ch == '_' {
 			ds := 1
 			if ch == '_' {
 				ds = 2
diff --git a/src/text/scanner/scanner_test.go b/src/text/scanner/scanner_test.go
index fb68106c16..fe39d3060b 100644
--- a/src/text/scanner/scanner_test.go
+++ b/src/text/scanner/scanner_test.go
@@ -886,8 +886,7 @@ func TestIssue30320(t *testing.T) {
 		{"foo01.bar31.xx-0-1-1-0", "01 31 0 1 1 0", ScanInts},
 		{"foo0/12/0/5.67", "0 12 0 5 67", ScanInts},
 		{"xxx1e0yyy", "1 0", ScanInts},
-		{"1_2", "1 2", ScanInts}, // don't consume _ as part of a number if not explicitly enabled
-		{"1_2", "1_2", ScanInts | AllowDigitSeparators},
+		{"1_2", "1_2", ScanInts},
 		{"xxx1.0yyy2e3ee", "1 0 2 3", ScanInts},
 		{"xxx1.0yyy2e3ee", "1.0 2e3", ScanFloats},
 	} {