diff --git a/src/pkg/big/int.go b/src/pkg/big/int.go
index b0dde1e6e37..db13d20f71c 100644
--- a/src/pkg/big/int.go
+++ b/src/pkg/big/int.go
@@ -302,7 +302,7 @@ func (x *Int) String() string {
 	return x.abs.decimalString()
 }
 
-func charset(ch int) string {
+func charset(ch rune) string {
 	switch ch {
 	case 'b':
 		return lowercaseDigits[0:2]
@@ -339,7 +339,7 @@ func writeMultiple(s fmt.State, text string, count int) {
 // output field width, space or zero padding, and left or
 // right justification.
 //
-func (x *Int) Format(s fmt.State, ch int) {
+func (x *Int) Format(s fmt.State, ch rune) {
 	cs := charset(ch)
 
 	// special cases
@@ -460,7 +460,7 @@ func (z *Int) scan(r io.RuneScanner, base int) (*Int, int, os.Error) {
 // Scan is a support routine for fmt.Scanner; it sets z to the value of
 // the scanned number. It accepts the formats 'b' (binary), 'o' (octal),
 // 'd' (decimal), 'x' (lowercase hexadecimal), and 'X' (uppercase hexadecimal).
-func (z *Int) Scan(s fmt.ScanState, ch int) os.Error {
+func (z *Int) Scan(s fmt.ScanState, ch rune) os.Error {
 	s.SkipSpace() // skip leading space characters
 	base := 0
 	switch ch {
diff --git a/src/pkg/big/nat.go b/src/pkg/big/nat.go
index c0769d88a91..fa0d7e72277 100644
--- a/src/pkg/big/nat.go
+++ b/src/pkg/big/nat.go
@@ -589,15 +589,15 @@ func (x nat) bitLen() int {
 // MaxBase is the largest number base accepted for string conversions.
 const MaxBase = 'z' - 'a' + 10 + 1 // = hexValue('z') + 1
 
-func hexValue(ch int) Word {
+func hexValue(ch rune) Word {
 	d := MaxBase + 1 // illegal base
 	switch {
 	case '0' <= ch && ch <= '9':
-		d = ch - '0'
+		d = int(ch - '0')
 	case 'a' <= ch && ch <= 'z':
-		d = ch - 'a' + 10
+		d = int(ch - 'a' + 10)
 	case 'A' <= ch && ch <= 'Z':
-		d = ch - 'A' + 10
+		d = int(ch - 'A' + 10)
 	}
 	return Word(d)
 }
diff --git a/src/pkg/big/nat_test.go b/src/pkg/big/nat_test.go
index 4f5732824c5..ab34c6ec189 100644
--- a/src/pkg/big/nat_test.go
+++ b/src/pkg/big/nat_test.go
@@ -231,7 +231,7 @@ var natScanTests = []struct {
 	x    nat    // expected nat
 	b    int    // expected base
 	ok   bool   // expected success
-	next int    // next character (or 0, if at EOF)
+	next rune   // next character (or 0, if at EOF)
 }{
 	// error: illegal base
 	{base: -1},
diff --git a/src/pkg/big/rat.go b/src/pkg/big/rat.go
index 6b860627206..1940a05494d 100644
--- a/src/pkg/big/rat.go
+++ b/src/pkg/big/rat.go
@@ -249,13 +249,13 @@ func (z *Rat) Quo(x, y *Rat) *Rat {
 	return z.norm()
 }
 
-func ratTok(ch int) bool {
+func ratTok(ch rune) bool {
 	return strings.IndexRune("+-/0123456789.eE", ch) >= 0
 }
 
 // Scan is a support routine for fmt.Scanner. It accepts the formats
 // 'e', 'E', 'f', 'F', 'g', 'G', and 'v'. All formats are equivalent.
-func (z *Rat) Scan(s fmt.ScanState, ch int) os.Error {
+func (z *Rat) Scan(s fmt.ScanState, ch rune) os.Error {
 	tok, err := s.Token(true, ratTok)
 	if err != nil {
 		return err