diff --git a/src/pkg/bignum/bignum.go b/src/pkg/bignum/bignum.go
index b9ea665..665ab9f 100755
--- a/src/pkg/bignum/bignum.go
+++ b/src/pkg/bignum/bignum.go
@@ -722,7 +722,7 @@
 // Format is a support routine for fmt.Formatter. It accepts
 // the formats 'b' (binary), 'o' (octal), and 'x' (hexadecimal).
 //
-func (x Natural) Format(h fmt.Formatter, c int) {
+func (x Natural) Format(h fmt.State, c int) {
 	fmt.Fprintf(h, "%s", x.ToString(fmtbase(c)));
 }
 
@@ -1252,7 +1252,7 @@
 // Format is a support routine for fmt.Formatter. It accepts
 // the formats 'b' (binary), 'o' (octal), and 'x' (hexadecimal).
 //
-func (x *Integer) Format(h fmt.Formatter, c int) {
+func (x *Integer) Format(h fmt.State, c int) {
 	fmt.Fprintf(h, "%s", x.ToString(fmtbase(c)));
 }
 
@@ -1424,7 +1424,7 @@
 // Format is a support routine for fmt.Formatter. It accepts
 // the formats 'b' (binary), 'o' (octal), and 'x' (hexadecimal).
 //
-func (x *Rational) Format(h fmt.Formatter, c int) {
+func (x *Rational) Format(h fmt.State, c int) {
 	fmt.Fprintf(h, "%s", x.ToString(fmtbase(c)));
 }
 
diff --git a/src/pkg/fmt/fmt_test.go b/src/pkg/fmt/fmt_test.go
index e8abc2f..d530a01 100644
--- a/src/pkg/fmt/fmt_test.go
+++ b/src/pkg/fmt/fmt_test.go
@@ -172,7 +172,7 @@
 }
 
 type flagPrinter struct { }
-func (*flagPrinter) Format(f fmt.Formatter, c int) {
+func (*flagPrinter) Format(f fmt.State, c int) {
 	s := "%";
 	for i := 0; i < 128; i++ {
 		if f.Flag(i) {
diff --git a/src/pkg/fmt/print.go b/src/pkg/fmt/print.go
index 7562ff1..2c5b739 100644
--- a/src/pkg/fmt/print.go
+++ b/src/pkg/fmt/print.go
@@ -74,10 +74,10 @@
 	"utf8";
 )
 
-// Formatter represents the printer state passed to custom formatters.
+// State represents the printer state passed to custom formatters.
 // It provides access to the io.Writer interface plus information about
 // the flags and options for the operand's format specifier.
-type Formatter interface {
+type State interface {
 	// Write is the function to call to emit formatted output to be printed.
 	Write(b []byte) (ret int, err os.Error);
 	// Width returns the value of the width option and whether it has been set.
@@ -92,8 +92,8 @@
 // Format is the interface implemented by objects with a custom formatter.
 // The implementation of Format may call Sprintf or Fprintf(f) etc.
 // to generate its output.
-type Format interface {
-	Format(f Formatter, c int);
+type Formatter interface {
+	Format(f State, c int);
 }
 
 // String represents any object being printed that has a String() method that
@@ -565,7 +565,7 @@
 		fieldnum++;
 		inter := field.Interface();
 		if inter != nil && c != 'T' {	// don't want thing to describe itself if we're asking for its type
-			if formatter, ok := inter.(Format); ok {
+			if formatter, ok := inter.(Formatter); ok {
 				formatter.Format(p, c);
 				continue;
 			}