diff --git a/cmd/stringer/golden_test.go b/cmd/stringer/golden_test.go
index 76e81c36..12df238f 100644
--- a/cmd/stringer/golden_test.go
+++ b/cmd/stringer/golden_test.go
@@ -51,7 +51,7 @@ const _Day_name = "MondayTuesdayWednesdayThursdayFridaySaturdaySunday"
 var _Day_index = [...]uint8{0, 6, 13, 22, 30, 36, 44, 50}
 
 func (i Day) String() string {
-	if i < 0 || i+1 >= Day(len(_Day_index)) {
+	if i < 0 || i >= Day(len(_Day_index)-1) {
 		return fmt.Sprintf("Day(%d)", i)
 	}
 	return _Day_name[_Day_index[i]:_Day_index[i+1]]
@@ -77,7 +77,7 @@ var _Number_index = [...]uint8{0, 3, 6, 11}
 
 func (i Number) String() string {
 	i -= 1
-	if i < 0 || i+1 >= Number(len(_Number_index)) {
+	if i < 0 || i >= Number(len(_Number_index)-1) {
 		return fmt.Sprintf("Number(%d)", i+1)
 	}
 	return _Number_name[_Number_index[i]:_Number_index[i+1]]
@@ -145,7 +145,7 @@ var _Num_index = [...]uint8{0, 3, 6, 8, 10, 12}
 
 func (i Num) String() string {
 	i -= -2
-	if i < 0 || i+1 >= Num(len(_Num_index)) {
+	if i < 0 || i >= Num(len(_Num_index)-1) {
 		return fmt.Sprintf("Num(%d)", i+-2)
 	}
 	return _Num_name[_Num_index[i]:_Num_index[i+1]]
diff --git a/cmd/stringer/stringer.go b/cmd/stringer/stringer.go
index 62941001..be87dec7 100644
--- a/cmd/stringer/stringer.go
+++ b/cmd/stringer/stringer.go
@@ -562,7 +562,7 @@ func (g *Generator) buildOneRun(runs [][]Value, typeName string) {
 //	[2]: size of index element (8 for uint8 etc.)
 //	[3]: less than zero check (for signed types)
 const stringOneRun = `func (i %[1]s) String() string {
-	if %[3]si+1 >= %[1]s(len(_%[1]s_index)) {
+	if %[3]si >= %[1]s(len(_%[1]s_index)-1) {
 		return fmt.Sprintf("%[1]s(%%d)", i)
 	}
 	return _%[1]s_name[_%[1]s_index[i]:_%[1]s_index[i+1]]
@@ -578,7 +578,7 @@ const stringOneRun = `func (i %[1]s) String() string {
  */
 const stringOneRunWithOffset = `func (i %[1]s) String() string {
 	i -= %[2]s
-	if %[4]si+1 >= %[1]s(len(_%[1]s_index)) {
+	if %[4]si >= %[1]s(len(_%[1]s_index)-1) {
 		return fmt.Sprintf("%[1]s(%%d)", i + %[2]s)
 	}
 	return _%[1]s_name[_%[1]s_index[i] : _%[1]s_index[i+1]]
diff --git a/cmd/stringer/testdata/unum2.go b/cmd/stringer/testdata/unum2.go
new file mode 100644
index 00000000..edbbedf3
--- /dev/null
+++ b/cmd/stringer/testdata/unum2.go
@@ -0,0 +1,31 @@
+// Copyright 2014 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.
+
+// Unsigned integers - check maximum size
+
+package main
+
+import "fmt"
+
+type Unum2 uint8
+
+const (
+	Zero Unum2 = iota
+	One
+	Two
+)
+
+func main() {
+	ck(Zero, "Zero")
+	ck(One, "One")
+	ck(Two, "Two")
+	ck(3, "Unum2(3)")
+	ck(255, "Unum2(255)")
+}
+
+func ck(unum Unum2, str string) {
+	if fmt.Sprint(unum) != str {
+		panic("unum.go: " + str)
+	}
+}