diff --git a/testdata/day.golden b/testdata/day.golden
index f23e69b..a79333d 100644
--- a/testdata/day.golden
+++ b/testdata/day.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 6, 13, 22, 30, 36, 44, 50}
 
 const _DayLowerName = "mondaytuesdaywednesdaythursdayfridaysaturdaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 func (Day) Values() []string {
diff --git a/testdata/dayTrimAndPrefix.golden b/testdata/dayTrimAndPrefix.golden
index 7f5367d..3160cab 100644
--- a/testdata/dayTrimAndPrefix.golden
+++ b/testdata/dayTrimAndPrefix.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 11, 23, 37, 50, 61, 74, 85}
 
 const _DayLowerName = "nightmondaynighttuesdaynightwednesdaynightthursdaynightfridaynightsaturdaynightsunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/dayWithLinecomment.golden b/testdata/dayWithLinecomment.golden
index c6b8584..d90b901 100644
--- a/testdata/dayWithLinecomment.golden
+++ b/testdata/dayWithLinecomment.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 5, 12, 21, 29, 36, 44, 50}
 
 const _DayLowerName = "lunestuesdaywednesdaythursdayviernessaturdaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/dayWithPrefix.golden b/testdata/dayWithPrefix.golden
index d468741..8dc17fa 100644
--- a/testdata/dayWithPrefix.golden
+++ b/testdata/dayWithPrefix.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 9, 19, 31, 42, 51, 62, 71}
 
 const _DayLowerName = "daymondaydaytuesdaydaywednesdaydaythursdaydayfridaydaysaturdaydaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/gap.golden b/testdata/gap.golden
index cc3e48d..6a54c83 100644
--- a/testdata/gap.golden
+++ b/testdata/gap.golden
@@ -25,7 +25,7 @@ func (i Gap) String() string {
 	case i == 11:
 		return _GapName_2
 	default:
-		return fmt.Sprintf("Gap(%d)", i)
+		return ""
 	}
 }
 
diff --git a/testdata/num.golden b/testdata/num.golden
index 97cc937..47d2ef4 100644
--- a/testdata/num.golden
+++ b/testdata/num.golden
@@ -5,12 +5,17 @@ var _NumIndex = [...]uint8{0, 3, 6, 8, 10, 12}
 
 const _NumLowerName = "m_2m_1m0m1m2"
 
-func (i Num) String() string {
+func (i Num) string() (string, error) {
 	i -= -2
 	if i < 0 || i >= Num(len(_NumIndex)-1) {
-		return fmt.Sprintf("Num(%d)", i+-2)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _NumName[_NumIndex[i]:_NumIndex[i+1]]
+	return _NumName[_NumIndex[i]:_NumIndex[i+1]], nil
+}
+
+func (i Num) String() string {
+	val, _ := i.string()
+	return val
 }
 
 func (Num) Values() []string {
diff --git a/testdata/offset.golden b/testdata/offset.golden
index 0e52817..d7983f2 100644
--- a/testdata/offset.golden
+++ b/testdata/offset.golden
@@ -5,12 +5,17 @@ var _NumberIndex = [...]uint8{0, 3, 6, 11}
 
 const _NumberLowerName = "onetwothree"
 
-func (i Number) String() string {
+func (i Number) string() (string, error) {
 	i -= 1
 	if i < 0 || i >= Number(len(_NumberIndex)-1) {
-		return fmt.Sprintf("Number(%d)", i+1)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _NumberName[_NumberIndex[i]:_NumberIndex[i+1]]
+	return _NumberName[_NumberIndex[i]:_NumberIndex[i+1]], nil
+}
+
+func (i Number) String() string {
+	val, _ := i.string()
+	return val
 }
 
 func (Number) Values() []string {
diff --git a/testdata/prime.golden b/testdata/prime.golden
index 8783338..3c54e43 100644
--- a/testdata/prime.golden
+++ b/testdata/prime.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 func (Prime) Values() []string {
diff --git a/testdata/primeGQLGen.golden b/testdata/primeGQLGen.golden
index 14c8eff..14822bc 100644
--- a/testdata/primeGQLGen.golden
+++ b/testdata/primeGQLGen.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/primeJson.golden b/testdata/primeJson.golden
index 9224728..beee577 100644
--- a/testdata/primeJson.golden
+++ b/testdata/primeJson.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/primeJsonAndSql.golden b/testdata/primeJsonAndSql.golden
index 1133b4a..27b5acb 100644
--- a/testdata/primeJsonAndSql.golden
+++ b/testdata/primeJsonAndSql.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
@@ -140,7 +145,7 @@ func (i *Prime) UnmarshalJSON(data []byte) error {
 }
 
 func (i Prime) Value() (driver.Value, error) {
-	return i.String(), nil
+	return i.string()
 }
 
 func (i *Prime) Scan(value interface{}) error {
diff --git a/testdata/primeSql.golden b/testdata/primeSql.golden
index 9a5292a..092fa70 100644
--- a/testdata/primeSql.golden
+++ b/testdata/primeSql.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
@@ -123,7 +128,7 @@ func (i Prime) IsAPrime() bool {
 }
 
 func (i Prime) Value() (driver.Value, error) {
-	return i.String(), nil
+	return i.string()
 }
 
 func (i *Prime) Scan(value interface{}) error {
diff --git a/testdata/primeText.golden b/testdata/primeText.golden
index e8102d6..1c4eb64 100644
--- a/testdata/primeText.golden
+++ b/testdata/primeText.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/primeYaml.golden b/testdata/primeYaml.golden
index 5197219..3b1b24e 100644
--- a/testdata/primeYaml.golden
+++ b/testdata/primeYaml.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
@@ -124,7 +129,7 @@ func (i Prime) IsAPrime() bool {
 
 // MarshalYAML implements a YAML Marshaler for Prime
 func (i Prime) MarshalYAML() (interface{}, error) {
-	return i.String(), nil
+	return i.string()
 }
 
 // UnmarshalYAML implements a YAML Unmarshaler for Prime
diff --git a/testdata/trimPrefix.golden b/testdata/trimPrefix.golden
index 52f063e..b919e75 100644
--- a/testdata/trimPrefix.golden
+++ b/testdata/trimPrefix.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 6, 13, 22, 30, 36, 44, 50}
 
 const _DayLowerName = "mondaytuesdaywednesdaythursdayfridaysaturdaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/trimPrefixMultiple.golden b/testdata/trimPrefixMultiple.golden
index 439ca92..1aa2d42 100644
--- a/testdata/trimPrefixMultiple.golden
+++ b/testdata/trimPrefixMultiple.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 6, 13, 22, 30, 36, 44, 50}
 
 const _DayLowerName = "mondaytuesdaywednesdaythursdayfridaysaturdaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/unum.golden b/testdata/unum.golden
index 9e413dc..d327701 100644
--- a/testdata/unum.golden
+++ b/testdata/unum.golden
@@ -19,7 +19,7 @@ func (i Unum) String() string {
 		i -= 253
 		return _UnumName_1[_UnumIndex_1[i]:_UnumIndex_1[i+1]]
 	default:
-		return fmt.Sprintf("Unum(%d)", i)
+		return ""
 	}
 }