diff --git a/misc/dashboard/builder/hg.go b/misc/dashboard/builder/hg.go
index b15a2e381cb..63062cca135 100644
--- a/misc/dashboard/builder/hg.go
+++ b/misc/dashboard/builder/hg.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"fmt"
 	"os"
 	"strconv"
 	"strings"
@@ -19,7 +20,7 @@ type Commit struct {
 func getCommit(rev string) (c Commit, err os.Error) {
 	defer func() {
 		if err != nil {
-			err = errf("getCommit: %s: %s", rev, err)
+			err = fmt.Errorf("getCommit: %s: %s", rev, err)
 		}
 	}()
 	parts, err := getCommitParts(rev)
diff --git a/misc/dashboard/builder/main.go b/misc/dashboard/builder/main.go
index 374374b9625..fa48e07f203 100644
--- a/misc/dashboard/builder/main.go
+++ b/misc/dashboard/builder/main.go
@@ -156,7 +156,7 @@ func NewBuilder(builder string) (*Builder, os.Error) {
 	if len(s) == 2 {
 		b.goos, b.goarch = s[0], s[1]
 	} else {
-		return nil, errf("unsupported builder form: %s", builder)
+		return nil, fmt.Errorf("unsupported builder form: %s", builder)
 	}
 
 	// read keys from keyfile
@@ -166,7 +166,7 @@ func NewBuilder(builder string) (*Builder, os.Error) {
 	}
 	c, err := ioutil.ReadFile(fn)
 	if err != nil {
-		return nil, errf("readKeys %s (%s): %s", b.name, fn, err)
+		return nil, fmt.Errorf("readKeys %s (%s): %s", b.name, fn, err)
 	}
 	v := strings.Split(string(c), "\n", -1)
 	b.key = v[0]
@@ -207,7 +207,7 @@ func (b *Builder) build() bool {
 func (b *Builder) nextCommit() (nextC *Commit, err os.Error) {
 	defer func() {
 		if err != nil {
-			err = errf("%s nextCommit: %s", b.name, err)
+			err = fmt.Errorf("%s nextCommit: %s", b.name, err)
 		}
 	}()
 	hw, err := b.getHighWater()
@@ -229,7 +229,7 @@ func (b *Builder) nextCommit() (nextC *Commit, err os.Error) {
 func (b *Builder) buildCommit(c Commit) (err os.Error) {
 	defer func() {
 		if err != nil {
-			err = errf("%s buildCommit: %d: %s", b.name, c.num, err)
+			err = fmt.Errorf("%s buildCommit: %d: %s", b.name, c.num, err)
 		}
 	}()
 
@@ -271,7 +271,7 @@ func (b *Builder) buildCommit(c Commit) (err os.Error) {
 	// build
 	buildLog, status, err := runLog(env, srcDir, *buildCmd)
 	if err != nil {
-		return errf("all.bash: %s", err)
+		return fmt.Errorf("all.bash: %s", err)
 	}
 	if status != 0 {
 		// record failure
@@ -280,7 +280,7 @@ func (b *Builder) buildCommit(c Commit) (err os.Error) {
 
 	// record success
 	if err = b.recordResult("", c); err != nil {
-		return errf("recordResult: %s", err)
+		return fmt.Errorf("recordResult: %s", err)
 	}
 
 	// send benchmark request if benchmarks are enabled
@@ -303,13 +303,13 @@ func (b *Builder) buildCommit(c Commit) (err os.Error) {
 		// clean out build state
 		err = run(env, srcDir, "./clean.bash", "--nopkg")
 		if err != nil {
-			return errf("clean.bash: %s", err)
+			return fmt.Errorf("clean.bash: %s", err)
 		}
 		// upload binary release
 		fn := fmt.Sprintf("%s.%s-%s.tar.gz", release, b.goos, b.goarch)
 		err = run(nil, workpath, "tar", "czf", fn, "go")
 		if err != nil {
-			return errf("tar: %s", err)
+			return fmt.Errorf("tar: %s", err)
 		}
 		err = run(nil, workpath, "python",
 			path.Join(goroot, codePyScript),
@@ -333,7 +333,3 @@ func isFile(name string) bool {
 	s, err := os.Stat(name)
 	return err == nil && (s.IsRegular() || s.IsSymlink())
 }
-
-func errf(format string, args ...interface{}) os.Error {
-	return os.NewError(fmt.Sprintf(format, args))
-}
diff --git a/src/pkg/go/printer/printer.go b/src/pkg/go/printer/printer.go
index cdc8cf518d2..f8b5871d09f 100644
--- a/src/pkg/go/printer/printer.go
+++ b/src/pkg/go/printer/printer.go
@@ -1091,7 +1091,7 @@ func (cfg *Config) Fprint(output io.Writer, node interface{}) (int, os.Error) {
 			p.useNodeComments = n.Comments == nil
 			p.file(n)
 		default:
-			p.errors <- os.NewError(fmt.Sprintf("printer.Fprint: unsupported node type %T", n))
+			p.errors <- fmt.Errorf("printer.Fprint: unsupported node type %T", n)
 			runtime.Goexit()
 		}
 		p.flush(token.Position{Offset: infinity, Line: infinity}, token.EOF)
diff --git a/src/pkg/image/png/writer_test.go b/src/pkg/image/png/writer_test.go
index f25873ebe56..0fb7bebaed0 100644
--- a/src/pkg/image/png/writer_test.go
+++ b/src/pkg/image/png/writer_test.go
@@ -15,14 +15,14 @@ import (
 func diff(m0, m1 image.Image) os.Error {
 	b0, b1 := m0.Bounds(), m1.Bounds()
 	if !b0.Eq(b1) {
-		return os.NewError(fmt.Sprintf("dimensions differ: %v vs %v", b0, b1))
+		return fmt.Errorf("dimensions differ: %v vs %v", b0, b1)
 	}
 	for y := b0.Min.Y; y < b0.Max.Y; y++ {
 		for x := b0.Min.X; x < b0.Max.X; x++ {
 			r0, g0, b0, a0 := m0.At(x, y).RGBA()
 			r1, g1, b1, a1 := m1.At(x, y).RGBA()
 			if r0 != r1 || g0 != g1 || b0 != b1 || a0 != a1 {
-				return os.NewError(fmt.Sprintf("colors differ at (%d, %d): %v vs %v", x, y, m0.At(x, y), m1.At(x, y)))
+				return fmt.Errorf("colors differ at (%d, %d): %v vs %v", x, y, m0.At(x, y), m1.At(x, y))
 			}
 		}
 	}
diff --git a/src/pkg/rpc/jsonrpc/client.go b/src/pkg/rpc/jsonrpc/client.go
index b34ffab056f..dcaa69f9dfc 100644
--- a/src/pkg/rpc/jsonrpc/client.go
+++ b/src/pkg/rpc/jsonrpc/client.go
@@ -87,7 +87,7 @@ func (c *clientCodec) ReadResponseHeader(r *rpc.Response) os.Error {
 	if c.resp.Error != nil {
 		x, ok := c.resp.Error.(string)
 		if !ok {
-			return os.NewError(fmt.Sprintf("invalid error %v", c.resp.Error))
+			return fmt.Errorf("invalid error %v", c.resp.Error)
 		}
 		if x == "" {
 			x = "unspecified error"