diff --git a/shiny/iconvg/decode_test.go b/shiny/iconvg/decode_test.go
index c1778e6..c06d816 100644
--- a/shiny/iconvg/decode_test.go
+++ b/shiny/iconvg/decode_test.go
@@ -14,6 +14,7 @@
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"testing"
 )
@@ -173,6 +174,54 @@
 	}
 }
 
+// The IconVG decoder and encoder are expected to be completely deterministic,
+// so check that we get the original bytes after a decode + encode round-trip.
+func TestDecodeEncodeRoundTrip(t *testing.T) {
+	for _, tc := range testdataTestCases {
+		ivgData, err := ioutil.ReadFile(filepath.FromSlash(tc.filename) + ".ivg")
+		if err != nil {
+			t.Errorf("%s: ReadFile: %v", tc.filename, err)
+			continue
+		}
+		var e resolutionPreservingEncoder
+		e.HighResolutionCoordinates = strings.HasSuffix(tc.filename, ".hires")
+		if err := Decode(&e, ivgData, nil); err != nil {
+			t.Errorf("%s: Decode: %v", tc.filename, err)
+			continue
+		}
+		got, err := e.Bytes()
+		if err != nil {
+			t.Errorf("%s: Encoder.Bytes: %v", tc.filename, err)
+			continue
+		}
+		if want := ivgData; !bytes.Equal(got, want) {
+			t.Errorf("%s:\ngot  %d bytes (on GOOS=%s GOARCH=%s, using compiler %q):\n% x\nwant %d bytes:\n% x",
+				tc.filename, len(got), runtime.GOOS, runtime.GOARCH, runtime.Compiler, got, len(want), want)
+			gotDisasm, err1 := disassemble(got)
+			wantDisasm, err2 := disassemble(want)
+			if err1 == nil && err2 == nil {
+				diffLines(t, string(gotDisasm), string(wantDisasm))
+			}
+		}
+	}
+}
+
+// resolutionPreservingEncoder is an Encoder
+// whose Reset method keeps prior resolution.
+type resolutionPreservingEncoder struct {
+	Encoder
+}
+
+// Reset resets the Encoder for the given Metadata.
+//
+// Unlike Encoder.Reset, it leaves the value
+// of e.HighResolutionCoordinates unmodified.
+func (e *resolutionPreservingEncoder) Reset(m Metadata) {
+	orig := e.HighResolutionCoordinates
+	e.Encoder.Reset(m)
+	e.HighResolutionCoordinates = orig
+}
+
 func TestDecodeAndRasterize(t *testing.T) {
 	for _, tc := range testdataTestCases {
 		ivgData, err := ioutil.ReadFile(filepath.FromSlash(tc.filename) + ".ivg")
diff --git a/shiny/iconvg/encode.go b/shiny/iconvg/encode.go
index 6c27f83..47e6a58 100644
--- a/shiny/iconvg/encode.go
+++ b/shiny/iconvg/encode.go
@@ -233,7 +233,7 @@
 	if e.err != nil {
 		return
 	}
-	if adj < 0 || 6 < adj {
+	if adj > 6 {
 		e.err = errInvalidSelectorAdjustment
 		return
 	}
@@ -272,7 +272,7 @@
 	if e.err != nil {
 		return
 	}
-	if adj < 0 || 6 < adj {
+	if adj > 6 {
 		e.err = errInvalidSelectorAdjustment
 		return
 	}
@@ -440,7 +440,7 @@
 	if e.err != nil {
 		return
 	}
-	if adj < 0 || 6 < adj {
+	if adj > 6 {
 		e.err = errInvalidSelectorAdjustment
 		return
 	}
diff --git a/shiny/iconvg/encode_test.go b/shiny/iconvg/encode_test.go
index 8c2592c..0f41f52 100644
--- a/shiny/iconvg/encode_test.go
+++ b/shiny/iconvg/encode_test.go
@@ -46,8 +46,13 @@
 		// to non-determinism in floating-point math, the encoder needs to be fixed.
 		//
 		// See golang.org/issue/43219#issuecomment-748531069.
-		t.Fatalf("\ngot  %d bytes (on GOOS=%s GOARCH=%s, using compiler %q):\n% x\nwant %d bytes:\n% x",
+		t.Errorf("\ngot  %d bytes (on GOOS=%s GOARCH=%s, using compiler %q):\n% x\nwant %d bytes:\n% x",
 			len(got), runtime.GOOS, runtime.GOARCH, runtime.Compiler, got, len(want), want)
+		gotDisasm, err1 := disassemble(got)
+		wantDisasm, err2 := disassemble(want)
+		if err1 == nil && err2 == nil {
+			diffLines(t, string(gotDisasm), string(wantDisasm))
+		}
 	}
 }