diff --git a/uniuri.go b/uniuri.go
index 7b6155f..c9898fd 100644
--- a/uniuri.go
+++ b/uniuri.go
@@ -51,7 +51,7 @@ func NewLenChars(length int, chars []byte) string {
 	i := 0
 	for {
 		if _, err := io.ReadFull(rand.Reader, r); err != nil {
-			panic("error reading from random source: " + err.String())
+			panic("error reading from random source: " + err.Error())
 		}
 		for _, c := range r {
 			if c >= maxrb {
diff --git a/uniuri_test.go b/uniuri_test.go
index 9899081..e43f213 100644
--- a/uniuri_test.go
+++ b/uniuri_test.go
@@ -12,7 +12,7 @@ func TestNew(t *testing.T) {
 	for _, c := range u {
 		var present bool
 		for _, a := range StdChars {
-			if int(a) == c {
+			if rune(a) == c {
 				present = true
 			}
 		}