diff --git a/pkg/blobserver/encrypt/encrypt.go b/pkg/blobserver/encrypt/encrypt.go
index 9c9340504..b7a67b094 100644
--- a/pkg/blobserver/encrypt/encrypt.go
+++ b/pkg/blobserver/encrypt/encrypt.go
@@ -273,7 +273,7 @@ func (s *storage) ReceiveBlob(plainBR blob.Ref, source io.Reader) (sb blob.Sized
 
 	err = s.index.Set(plainBR.String(), meta)
 	if err != nil {
-		return sb, fmt.Errorf("encrypt: error updating index for encrypted %v (plaintext %v): %v", err)
+		return sb, fmt.Errorf("encrypt: error updating index for encrypted %v (plaintext %v): %v", encBR, plainBR, err)
 	}
 
 	return blob.SizedRef{plainBR, uint32(plainSize)}, nil
diff --git a/pkg/blobserver/localdisk/upgrade32.go b/pkg/blobserver/localdisk/upgrade32.go
index 3010eb4e9..12cf88f5d 100644
--- a/pkg/blobserver/localdisk/upgrade32.go
+++ b/pkg/blobserver/localdisk/upgrade32.go
@@ -86,7 +86,7 @@ func (ds *DiskStorage) migrate3to2() error {
 			}
 			dst := ds.blobPath(br)
 			if fi, err := os.Stat(dst); !os.IsNotExist(err) {
-				return fmt.Errorf("Expected %s to not exist; got stat %v, %v", fi, err)
+				return fmt.Errorf("Expected %s to not exist; got stat %v, %v", dst, fi, err)
 			}
 			if err := os.Rename(path, dst); err != nil {
 				return err
diff --git a/pkg/blobserver/storagetest/storagetest.go b/pkg/blobserver/storagetest/storagetest.go
index c268009c6..c8de4b3b0 100644
--- a/pkg/blobserver/storagetest/storagetest.go
+++ b/pkg/blobserver/storagetest/storagetest.go
@@ -150,7 +150,7 @@ func testSizedBlob(t *testing.T, r io.Reader, b1 blob.Ref, size int64) {
 		t.Fatalf("error reading from %s: %v", r, err)
 	}
 	if n != size {
-		t.Fatalf("read %d bytes from %s, metadata said %d!", n, size)
+		t.Fatalf("read %d bytes from %s, metadata said %d!", n, r, size)
 	}
 	b2 := blob.RefFromHash(h)
 	if b2 != b1 {
diff --git a/pkg/importer/twitter/twitter.go b/pkg/importer/twitter/twitter.go
index 5f0727be9..9b7b9fde1 100644
--- a/pkg/importer/twitter/twitter.go
+++ b/pkg/importer/twitter/twitter.go
@@ -456,7 +456,7 @@ func (r *run) importTweet(parent *importer.Object, tweet tweetItem, viaAPI bool)
 			tried++
 			res, err := r.HTTPClient().Get(mediaURL)
 			if err != nil {
-				return false, fmt.Errorf("Error fetching %s for tweet %s : %v", mediaURL, url)
+				return false, fmt.Errorf("Error fetching %s for tweet %s : %v", mediaURL, url, err)
 			}
 			if res.StatusCode == http.StatusNotFound {
 				continue
diff --git a/pkg/media/audio.go b/pkg/media/audio.go
index 695ad7ced..2611c9af1 100644
--- a/pkg/media/audio.go
+++ b/pkg/media/audio.go
@@ -42,7 +42,7 @@ func HasID3v1Tag(r types.SizeReaderAt) (bool, error) {
 
 	buf := make([]byte, len(id3v1Magic), len(id3v1Magic))
 	if _, err := r.ReadAt(buf, r.Size()-ID3v1TagLength); err != nil {
-		return false, fmt.Errorf("Failed to read ID3v1 data: ", err)
+		return false, fmt.Errorf("Failed to read ID3v1 data: %v", err)
 	}
 	if bytes.Equal(buf, id3v1Magic) {
 		return true, nil
diff --git a/pkg/misc/amazon/s3/auth_test.go b/pkg/misc/amazon/s3/auth_test.go
index 6aee9e2ea..9ad84ac47 100644
--- a/pkg/misc/amazon/s3/auth_test.go
+++ b/pkg/misc/amazon/s3/auth_test.go
@@ -31,7 +31,7 @@ type reqAndExpected struct {
 func req(s string) *http.Request {
 	req, err := http.ReadRequest(bufio.NewReader(strings.NewReader(s)))
 	if err != nil {
-		panic(fmt.Sprintf("bad request in test: %q (error: %v)", req, err))
+		panic(fmt.Sprintf("bad request in test: %v (error: %v)", req, err))
 	}
 	return req
 }
diff --git a/pkg/misc/closure/gendeps.go b/pkg/misc/closure/gendeps.go
index b94f72109..69178c247 100644
--- a/pkg/misc/closure/gendeps.go
+++ b/pkg/misc/closure/gendeps.go
@@ -185,7 +185,7 @@ func ParseDeps(r io.Reader) (providedBy map[string]string, requires map[string][
 			}
 			providedBy[namespace] = jsfile
 			if _, ok := requires[namespace]; ok {
-				return nil, nil, fmt.Errorf("Name %v has two sets of dependencies")
+				return nil, nil, fmt.Errorf("Name %v has two sets of dependencies", namespace)
 			}
 			if required != nil {
 				requires[namespace] = required
diff --git a/pkg/netutil/ident.go b/pkg/netutil/ident.go
index d144bd4d8..1776b25d8 100644
--- a/pkg/netutil/ident.go
+++ b/pkg/netutil/ident.go
@@ -55,7 +55,7 @@ func HostPortToIP(hostport string, ctx *net.TCPAddr) (hostaddr *net.TCPAddr, err
 	}
 	iport, err := strconv.Atoi(port)
 	if err != nil || iport < 0 || iport > 0xFFFF {
-		return nil, fmt.Errorf("invalid port %s", iport)
+		return nil, fmt.Errorf("invalid port %d", iport)
 	}
 	var addr net.IP
 	if ctx != nil && host == "localhost" {
diff --git a/pkg/schema/filewriter.go b/pkg/schema/filewriter.go
index 8fd428ddb..946612edd 100644
--- a/pkg/schema/filewriter.go
+++ b/pkg/schema/filewriter.go
@@ -106,7 +106,7 @@ func writeFileMapOld(bs blobserver.StatReceiver, file *Builder, r io.Reader) (bl
 				return blob.Ref{}, err
 			}
 			if want := (blob.SizedRef{br, uint32(n)}); sb != want {
-				return blob.Ref{}, fmt.Errorf("schema/filewriter: wrote %s, expect", sb, want)
+				return blob.Ref{}, fmt.Errorf("schema/filewriter: wrote %s, expect %s", sb, want)
 			}
 		}
 
diff --git a/pkg/singleflight/singleflight_test.go b/pkg/singleflight/singleflight_test.go
index b75b608b4..40edcf30b 100644
--- a/pkg/singleflight/singleflight_test.go
+++ b/pkg/singleflight/singleflight_test.go
@@ -45,7 +45,7 @@ func TestDoErr(t *testing.T) {
 		return nil, someErr
 	})
 	if err != someErr {
-		t.Errorf("Do error = %v; want someErr", err, someErr)
+		t.Errorf("Do error = %v; want someErr %v", err, someErr)
 	}
 	if v != nil {
 		t.Errorf("unexpected non-nil value %#v", v)
diff --git a/pkg/types/types.go b/pkg/types/types.go
index aa08f7fa3..61eb40409 100644
--- a/pkg/types/types.go
+++ b/pkg/types/types.go
@@ -71,7 +71,7 @@ func (t *Time3339) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	if len(b) < 2 || b[0] != '"' || b[len(b)-1] != '"' {
-		return fmt.Errorf("types: failed to unmarshal non-string value %q as an RFC 3339 time")
+		return fmt.Errorf("types: failed to unmarshal non-string value %q as an RFC 3339 time", b)
 	}
 	s := string(b[1 : len(b)-1])
 	if s == "" {