diff --git a/src/encoding/hex/hex.go b/src/encoding/hex/hex.go
index 5a8243ae80..f69abb2f7f 100644
--- a/src/encoding/hex/hex.go
+++ b/src/encoding/hex/hex.go
@@ -75,9 +75,6 @@ func DecodedLen(x int) int { return x / 2 }
 // If the input is malformed, Decode returns the number
 // of bytes decoded before the error.
 func Decode(dst, src []byte) (int, error) {
-	if len(dst) < DecodedLen(len(src)) {
-		return 0, errors.New("encoding/hex: output buffer too small")
-	}
 	i, j := 0, 1
 	for ; j < len(src); j += 2 {
 		p := src[j-1]
@@ -91,6 +88,9 @@ func Decode(dst, src []byte) (int, error) {
 		if b > 0x0f {
 			return i, InvalidByteError(q)
 		}
+		if i >= len(dst) {
+			return i, errors.New("encoding/hex: output buffer too small")
+		}
 		dst[i] = (a << 4) | b
 		i++
 	}
diff --git a/src/encoding/hex/hex_test.go b/src/encoding/hex/hex_test.go
index 1eb169cdee..8d1ae70774 100644
--- a/src/encoding/hex/hex_test.go
+++ b/src/encoding/hex/hex_test.go
@@ -55,13 +55,16 @@ func TestDecode(t *testing.T) {
 	}
 }
 
-func TestDecode_tooFewDstBytes(t *testing.T) {
+func TestDecodeDstTooSmall(t *testing.T) {
 	dst := make([]byte, 1)
 	src := []byte{'0', '1', '2', '3'}
-	_, err := Decode(dst, src)
+	n, err := Decode(dst, src)
 	if err == nil {
 		t.Errorf("expected Decode to return an error, but it returned none")
 	}
+	if !bytes.Equal(dst[:n], []byte{0x01}) {
+		t.Errorf("output mismatch: got %x, want 01", dst[:n])
+	}
 }
 
 func TestEncodeToString(t *testing.T) {