diff --git a/attributes.go b/attributes.go
index ed4a9b6..f4cf261 100644
--- a/attributes.go
+++ b/attributes.go
@@ -162,19 +162,34 @@ func (m *Message) Get(t AttrType) ([]byte, error) {
 	return v.Value, nil
 }
 
-// AttrLengthError occurs when len(v) > Max.
-type AttrLengthError struct {
+// AttrOverflowErr occurs when len(v) > Max.
+type AttrOverflowErr struct {
 	Type AttrType
 	Max  int
 	Got  int
 }
 
-func (e AttrLengthError) Error() string {
+func (e AttrOverflowErr) Error() string {
 	return fmt.Sprintf("Length of %s attribute %d exceeds maximum %d",
 		e.Type, e.Got, e.Max,
 	)
 }
 
+// AttrLengthErr means that length for attribute is invalid.
+type AttrLengthErr struct {
+	Attr     AttrType
+	Got      int
+	Expected int
+}
+
+func (e AttrLengthErr) Error() string {
+	return fmt.Sprintf("incorrect length for %s: got %d, expected %d",
+		e.Attr,
+		e.Got,
+		e.Expected,
+	)
+}
+
 // STUN aligns attributes on 32-bit boundaries, attributes whose content
 // is not a multiple of 4 bytes are padded with 1, 2, or 3 bytes of
 // padding so that its value contains a multiple of 4 bytes.  The
diff --git a/attributes_test.go b/attributes_test.go
index 4612cae..9716769 100644
--- a/attributes_test.go
+++ b/attributes_test.go
@@ -61,7 +61,7 @@ func TestPadding(t *testing.T) {
 }
 
 func TestAttrLengthError_Error(t *testing.T) {
-	err := AttrLengthError{
+	err := AttrOverflowErr{
 		Got:  100,
 		Max:  50,
 		Type: AttrLifetime,
diff --git a/errorcode.go b/errorcode.go
index 04fd592..2de37db 100644
--- a/errorcode.go
+++ b/errorcode.go
@@ -34,7 +34,11 @@ var ErrReasonLengthTooBig = errors.New("reason for ERROR-CODE is too big")
 func (c ErrorCodeAttribute) AddTo(m *Message) error {
 	value := make([]byte, 0, errorCodeReasonMaxB)
 	if len(c.Reason) > errorCodeReasonMaxB {
-		return ErrReasonLengthTooBig
+		return &AttrOverflowErr{
+			Got:  len(c.Reason) + errorCodeReasonStart,
+			Max:  errorCodeReasonMaxB + errorCodeReasonStart,
+			Type: AttrErrorCode,
+		}
 	}
 	value = value[:errorCodeReasonStart+len(c.Reason)]
 	number := byte(c.Code % errorCodeModulo) // error code modulo 100
diff --git a/fingerprint.go b/fingerprint.go
index cedcf07..633934c 100644
--- a/fingerprint.go
+++ b/fingerprint.go
@@ -68,10 +68,11 @@ func (FingerprintAttr) Check(m *Message) error {
 		return err
 	}
 	if len(b) != fingerprintSize {
-		return newDecodeErr("message",
-			"fingerprint",
-			"bad length",
-		)
+		return &AttrLengthErr{
+			Expected: fingerprintSize,
+			Got:      len(b),
+			Attr:     AttrFingerprint,
+		}
 	}
 	val := bin.Uint32(b)
 	attrStart := len(m.Raw) - (fingerprintSize + attributeHeaderSize)
diff --git a/fuzz.go b/fuzz.go
index 5531710..e11265e 100644
--- a/fuzz.go
+++ b/fuzz.go
@@ -118,6 +118,10 @@ func FuzzSetters(data []byte) int {
 		// We allow decoding some text attributes
 		// when their length is too big, but
 		// not encoding.
+		_, ok := err.(*AttrOverflowErr)
+		if !ok {
+			panic(err)
+		}
 		return 1
 	}
 	m3.WriteHeader()
diff --git a/textattrs.go b/textattrs.go
index 5f0e228..ca77a95 100644
--- a/textattrs.go
+++ b/textattrs.go
@@ -113,7 +113,7 @@ type TextAttribute []byte
 // is less than 0, no check is performed.
 func (v TextAttribute) AddToAs(m *Message, t AttrType, maxLen int) error {
 	if maxLen > 0 && len(v) > maxLen {
-		return &AttrLengthError{
+		return &AttrOverflowErr{
 			Max:  maxLen,
 			Got:  len(v),
 			Type: t,
diff --git a/textattrs_test.go b/textattrs_test.go
index e64de9e..c09c09d 100644
--- a/textattrs_test.go
+++ b/textattrs_test.go
@@ -38,8 +38,8 @@ func TestSoftware_GetFrom(t *testing.T) {
 func TestSoftware_AddTo_Invalid(t *testing.T) {
 	m := New()
 	s := make(Software, 1024)
-	if err, ok := s.AddTo(m).(*AttrLengthError); !ok {
-		t.Errorf("AddTo should return *AttrLengthError, got: %v", err)
+	if err, ok := s.AddTo(m).(*AttrOverflowErr); !ok {
+		t.Errorf("AddTo should return *AttrOverflowErr, got: %v", err)
 	}
 	if err := s.GetFrom(m); err != ErrAttributeNotFound {
 		t.Errorf("GetFrom should return %q, got: %v", ErrAttributeNotFound, err)
@@ -87,7 +87,7 @@ func TestUsername(t *testing.T) {
 	m.WriteHeader()
 	t.Run("Bad length", func(t *testing.T) {
 		badU := make(Username, 600)
-		if err, ok := badU.AddTo(m).(*AttrLengthError); !ok {
+		if err, ok := badU.AddTo(m).(*AttrOverflowErr); !ok {
 			t.Errorf("expected length error, got %v", err)
 		}
 	})
@@ -163,8 +163,8 @@ func TestRealm_GetFrom(t *testing.T) {
 func TestRealm_AddTo_Invalid(t *testing.T) {
 	m := New()
 	r := make(Realm, 1024)
-	if err, ok := r.AddTo(m).(*AttrLengthError); !ok || err.Type != AttrRealm {
-		t.Errorf("AddTo should return *AttrLengthError, got: %v", err)
+	if err, ok := r.AddTo(m).(*AttrOverflowErr); !ok || err.Type != AttrRealm {
+		t.Errorf("AddTo should return *AttrOverflowErr, got: %v", err)
 	}
 	if err := r.GetFrom(m); err != ErrAttributeNotFound {
 		t.Errorf("GetFrom should return %q, got: %v", ErrAttributeNotFound, err)
@@ -204,8 +204,8 @@ func TestNonce_GetFrom(t *testing.T) {
 func TestNonce_AddTo_Invalid(t *testing.T) {
 	m := New()
 	n := make(Nonce, 1024)
-	if err, ok := n.AddTo(m).(*AttrLengthError); !ok || err.Type != AttrNonce {
-		t.Errorf("AddTo should return *AttrLengthError, got: %v", err)
+	if err, ok := n.AddTo(m).(*AttrOverflowErr); !ok || err.Type != AttrNonce {
+		t.Errorf("AddTo should return *AttrOverflowErr, got: %v", err)
 	}
 	if err := n.GetFrom(m); err != ErrAttributeNotFound {
 		t.Errorf("GetFrom should return %q, got: %v", ErrAttributeNotFound, err)