diff --git a/.travis.yml b/.travis.yml
index 7bd3a05..5919f98 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,8 +4,8 @@ matrix:
   allow_failures:
   - go: master
   include:
-  - go: 1.14.x
   - go: 1.15.x
+  - go: 1.16.x
   - go: master
 env:
   global:
@@ -24,6 +24,6 @@ deploy:
   - cli/build/enumer.windows-amd64.exe.tar.gz
   - cli/build/sha256sum.txt
   on:
-    go: 1.15.x
+    go: 1.16.x
     repo: dmarkham/enumer
     tags: true
diff --git a/README.md b/README.md
index 24e4376..7f5e78e 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Enumer [![GoDoc](https://godoc.org/github.com/dmarkham/enumer?status.svg)](https://godoc.org/github.com/dmarkham/enumer) [![Go Report Card](https://goreportcard.com/badge/github.com/dmarkham/enumer)](https://goreportcard.com/report/github.com/dmarkham/enumer) [![GitHub Release](https://img.shields.io/github/release/dmarkham/enumer.svg)](https://github.com/dmarkham/enumer/releases)[![Build Status](https://travis-ci.org/dmarkham/enumer.svg?branch=master)](https://travis-ci.org/dmarkham/enumer)
+# Enumer [![GoDoc](https://godoc.org/github.com/dmarkham/enumer?status.svg)](https://godoc.org/github.com/dmarkham/enumer) [![Go Report Card](https://goreportcard.com/badge/github.com/dmarkham/enumer)](https://goreportcard.com/report/github.com/dmarkham/enumer) [![GitHub Release](https://img.shields.io/github/release/dmarkham/enumer.svg)](https://github.com/dmarkham/enumer/releases)[![Build Status](https://travis-ci.com/dmarkham/enumer.svg?branch=master)](https://travis-ci.com/dmarkham/enumer)
 
 
 Enumer is a tool to generate Go code that adds useful methods to Go enums (constants with a specific type).
diff --git a/enumer.go b/enumer.go
index 3cb1f5d..cfdc3a2 100644
--- a/enumer.go
+++ b/enumer.go
@@ -10,8 +10,8 @@ func %[1]sString(s string) (%[1]s, error) {
 	if val, ok := _%[1]sNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _%[1]sNameToValueMap[s]; ok {
+
+	if val, ok := _%[1]sNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%%s does not belong to %[1]s values", s)
diff --git a/testdata/day.golden b/testdata/day.golden
index fd4a481..537b04b 100644
--- a/testdata/day.golden
+++ b/testdata/day.golden
@@ -60,8 +60,8 @@ func DayString(s string) (Day, error) {
 	if val, ok := _DayNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _DayNameToValueMap[s]; ok {
+
+	if val, ok := _DayNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Day values", s)
diff --git a/testdata/dayTrimAndPrefix.golden b/testdata/dayTrimAndPrefix.golden
index c3afe9e..7f5367d 100644
--- a/testdata/dayTrimAndPrefix.golden
+++ b/testdata/dayTrimAndPrefix.golden
@@ -60,8 +60,8 @@ func DayString(s string) (Day, error) {
 	if val, ok := _DayNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _DayNameToValueMap[s]; ok {
+
+	if val, ok := _DayNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Day values", s)
diff --git a/testdata/dayWithLinecomment.golden b/testdata/dayWithLinecomment.golden
index 6b5dfdb..c6b8584 100644
--- a/testdata/dayWithLinecomment.golden
+++ b/testdata/dayWithLinecomment.golden
@@ -60,8 +60,8 @@ func DayString(s string) (Day, error) {
 	if val, ok := _DayNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _DayNameToValueMap[s]; ok {
+
+	if val, ok := _DayNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Day values", s)
diff --git a/testdata/dayWithPrefix.golden b/testdata/dayWithPrefix.golden
index 03a9280..d468741 100644
--- a/testdata/dayWithPrefix.golden
+++ b/testdata/dayWithPrefix.golden
@@ -60,8 +60,8 @@ func DayString(s string) (Day, error) {
 	if val, ok := _DayNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _DayNameToValueMap[s]; ok {
+
+	if val, ok := _DayNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Day values", s)
diff --git a/testdata/gap.golden b/testdata/gap.golden
index 6561679..129891e 100644
--- a/testdata/gap.golden
+++ b/testdata/gap.golden
@@ -81,8 +81,8 @@ func GapString(s string) (Gap, error) {
 	if val, ok := _GapNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _GapNameToValueMap[s]; ok {
+
+	if val, ok := _GapNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Gap values", s)
diff --git a/testdata/num.golden b/testdata/num.golden
index f496953..1a5407f 100644
--- a/testdata/num.golden
+++ b/testdata/num.golden
@@ -53,8 +53,8 @@ func NumString(s string) (Num, error) {
 	if val, ok := _NumNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _NumNameToValueMap[s]; ok {
+
+	if val, ok := _NumNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Num values", s)
diff --git a/testdata/offset.golden b/testdata/offset.golden
index 69e91a9..44cc102 100644
--- a/testdata/offset.golden
+++ b/testdata/offset.golden
@@ -45,8 +45,8 @@ func NumberString(s string) (Number, error) {
 	if val, ok := _NumberNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _NumberNameToValueMap[s]; ok {
+
+	if val, ok := _NumberNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Number values", s)
diff --git a/testdata/prime.golden b/testdata/prime.golden
index 1719eac..283dbd1 100644
--- a/testdata/prime.golden
+++ b/testdata/prime.golden
@@ -97,8 +97,8 @@ func PrimeString(s string) (Prime, error) {
 	if val, ok := _PrimeNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _PrimeNameToValueMap[s]; ok {
+
+	if val, ok := _PrimeNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Prime values", s)
diff --git a/testdata/primeGQLGen.golden b/testdata/primeGQLGen.golden
index 3ff7ba5..14c8eff 100644
--- a/testdata/primeGQLGen.golden
+++ b/testdata/primeGQLGen.golden
@@ -97,8 +97,8 @@ func PrimeString(s string) (Prime, error) {
 	if val, ok := _PrimeNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _PrimeNameToValueMap[s]; ok {
+
+	if val, ok := _PrimeNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Prime values", s)
diff --git a/testdata/primeJson.golden b/testdata/primeJson.golden
index 8b1e82f..9224728 100644
--- a/testdata/primeJson.golden
+++ b/testdata/primeJson.golden
@@ -97,8 +97,8 @@ func PrimeString(s string) (Prime, error) {
 	if val, ok := _PrimeNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _PrimeNameToValueMap[s]; ok {
+
+	if val, ok := _PrimeNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Prime values", s)
diff --git a/testdata/primeJsonAndSql.golden b/testdata/primeJsonAndSql.golden
index 8449e6a..1133b4a 100644
--- a/testdata/primeJsonAndSql.golden
+++ b/testdata/primeJsonAndSql.golden
@@ -97,8 +97,8 @@ func PrimeString(s string) (Prime, error) {
 	if val, ok := _PrimeNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _PrimeNameToValueMap[s]; ok {
+
+	if val, ok := _PrimeNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Prime values", s)
diff --git a/testdata/primeSql.golden b/testdata/primeSql.golden
index d12a764..9a5292a 100644
--- a/testdata/primeSql.golden
+++ b/testdata/primeSql.golden
@@ -97,8 +97,8 @@ func PrimeString(s string) (Prime, error) {
 	if val, ok := _PrimeNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _PrimeNameToValueMap[s]; ok {
+
+	if val, ok := _PrimeNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Prime values", s)
diff --git a/testdata/primeText.golden b/testdata/primeText.golden
index d0f67cf..e8102d6 100644
--- a/testdata/primeText.golden
+++ b/testdata/primeText.golden
@@ -97,8 +97,8 @@ func PrimeString(s string) (Prime, error) {
 	if val, ok := _PrimeNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _PrimeNameToValueMap[s]; ok {
+
+	if val, ok := _PrimeNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Prime values", s)
diff --git a/testdata/primeYaml.golden b/testdata/primeYaml.golden
index 555c53c..5197219 100644
--- a/testdata/primeYaml.golden
+++ b/testdata/primeYaml.golden
@@ -97,8 +97,8 @@ func PrimeString(s string) (Prime, error) {
 	if val, ok := _PrimeNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _PrimeNameToValueMap[s]; ok {
+
+	if val, ok := _PrimeNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Prime values", s)
diff --git a/testdata/trimPrefix.golden b/testdata/trimPrefix.golden
index 77db514..52f063e 100644
--- a/testdata/trimPrefix.golden
+++ b/testdata/trimPrefix.golden
@@ -60,8 +60,8 @@ func DayString(s string) (Day, error) {
 	if val, ok := _DayNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _DayNameToValueMap[s]; ok {
+
+	if val, ok := _DayNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Day values", s)
diff --git a/testdata/trimPrefixMultiple.golden b/testdata/trimPrefixMultiple.golden
index b40e6f0..439ca92 100644
--- a/testdata/trimPrefixMultiple.golden
+++ b/testdata/trimPrefixMultiple.golden
@@ -60,8 +60,8 @@ func DayString(s string) (Day, error) {
 	if val, ok := _DayNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _DayNameToValueMap[s]; ok {
+
+	if val, ok := _DayNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Day values", s)
diff --git a/testdata/unum.golden b/testdata/unum.golden
index f496594..ed149b5 100644
--- a/testdata/unum.golden
+++ b/testdata/unum.golden
@@ -63,8 +63,8 @@ func UnumString(s string) (Unum, error) {
 	if val, ok := _UnumNameToValueMap[s]; ok {
 		return val, nil
 	}
-	s = strings.ToLower(s)
-	if val, ok := _UnumNameToValueMap[s]; ok {
+
+	if val, ok := _UnumNameToValueMap[strings.ToLower(s)]; ok {
 		return val, nil
 	}
 	return 0, fmt.Errorf("%s does not belong to Unum values", s)