diff --git a/error.go b/error.go
index b9d6452..3c2559e 100644
--- a/error.go
+++ b/error.go
@@ -192,6 +192,8 @@ func (e *Error) Error() string {
 	return fmt.Sprintf("LDAP Result Code %d %q: %s", e.ResultCode, LDAPResultCodeMap[e.ResultCode], e.Err.Error())
 }
 
+func (e *Error) Unwrap() error { return e.Err }
+
 // GetLDAPError creates an Error out of a BER packet representing a LDAPResult
 // The return is an error object. It can be casted to a Error structure.
 // This function returns nil if resultCode in the LDAPResult sequence is success(0).
diff --git a/error_test.go b/error_test.go
index 63018ee..c115e00 100644
--- a/error_test.go
+++ b/error_test.go
@@ -2,6 +2,7 @@ package ldap
 
 import (
 	"errors"
+	"io"
 	"net"
 	"strings"
 	"testing"
@@ -103,6 +104,24 @@ func TestGetLDAPErrorInvalidResponse(t *testing.T) {
 	}
 }
 
+func TestErrorIs(t *testing.T) {
+	err := NewError(ErrorNetwork, io.EOF)
+	if !errors.Is(err, io.EOF) {
+		t.Errorf("Expected an io.EOF error: %v", err)
+	}
+}
+
+func TestErrorAs(t *testing.T) {
+	var netErr net.InvalidAddrError = "invalid addr"
+	err := NewError(ErrorNetwork, netErr)
+
+	var target net.InvalidAddrError
+	ok := errors.As(err, &target)
+	if !ok {
+		t.Error("Expected an InvalidAddrError")
+	}
+}
+
 // TestGetLDAPErrorSuccess tests parsing of a result with no error (resultCode == 0).
 func TestGetLDAPErrorSuccess(t *testing.T) {
 	bindResponse := ber.Encode(ber.ClassApplication, ber.TypeConstructed, ApplicationBindResponse, nil, "Bind Response")
diff --git a/v3/control.go b/v3/control.go
index 6710feb..c2c3f87 100644
--- a/v3/control.go
+++ b/v3/control.go
@@ -928,9 +928,12 @@ func (c *ControlSyncRequest) GetControlType() string {
 func (c *ControlSyncRequest) Encode() *ber.Packet {
 	_mode := int64(c.Mode)
 	mode := ber.NewInteger(ber.ClassUniversal, ber.TypePrimitive, ber.TagEnumerated, _mode, "Mode")
-	cookie := ber.Encode(ber.ClassUniversal, ber.TypePrimitive, ber.TagOctetString, nil, "Cookie")
-	cookie.Value = c.Cookie
-	cookie.Data.Write(c.Cookie)
+	var cookie *ber.Packet
+	if len(c.Cookie) > 0 {
+		cookie = ber.Encode(ber.ClassUniversal, ber.TypePrimitive, ber.TagOctetString, nil, "Cookie")
+		cookie.Value = c.Cookie
+		cookie.Data.Write(c.Cookie)
+	}
 	reloadHint := ber.NewBoolean(ber.ClassUniversal, ber.TypePrimitive, ber.TagBoolean, c.ReloadHint, "Reload Hint")
 
 	packet := ber.Encode(ber.ClassUniversal, ber.TypeConstructed, ber.TagSequence, nil, "Control")
@@ -940,7 +943,9 @@ func (c *ControlSyncRequest) Encode() *ber.Packet {
 	val := ber.Encode(ber.ClassUniversal, ber.TypePrimitive, ber.TagOctetString, nil, "Control Value (Sync Request)")
 	seq := ber.Encode(ber.ClassUniversal, ber.TypeConstructed, ber.TagSequence, nil, "Sync Request Value")
 	seq.AppendChild(mode)
-	seq.AppendChild(cookie)
+	if cookie != nil {
+		seq.AppendChild(cookie)
+	}
 	seq.AppendChild(reloadHint)
 	val.AppendChild(seq)
 
diff --git a/v3/error.go b/v3/error.go
index b9d6452..3c2559e 100644
--- a/v3/error.go
+++ b/v3/error.go
@@ -192,6 +192,8 @@ func (e *Error) Error() string {
 	return fmt.Sprintf("LDAP Result Code %d %q: %s", e.ResultCode, LDAPResultCodeMap[e.ResultCode], e.Err.Error())
 }
 
+func (e *Error) Unwrap() error { return e.Err }
+
 // GetLDAPError creates an Error out of a BER packet representing a LDAPResult
 // The return is an error object. It can be casted to a Error structure.
 // This function returns nil if resultCode in the LDAPResult sequence is success(0).
diff --git a/v3/error_test.go b/v3/error_test.go
index 63018ee..c115e00 100644
--- a/v3/error_test.go
+++ b/v3/error_test.go
@@ -2,6 +2,7 @@ package ldap
 
 import (
 	"errors"
+	"io"
 	"net"
 	"strings"
 	"testing"
@@ -103,6 +104,24 @@ func TestGetLDAPErrorInvalidResponse(t *testing.T) {
 	}
 }
 
+func TestErrorIs(t *testing.T) {
+	err := NewError(ErrorNetwork, io.EOF)
+	if !errors.Is(err, io.EOF) {
+		t.Errorf("Expected an io.EOF error: %v", err)
+	}
+}
+
+func TestErrorAs(t *testing.T) {
+	var netErr net.InvalidAddrError = "invalid addr"
+	err := NewError(ErrorNetwork, netErr)
+
+	var target net.InvalidAddrError
+	ok := errors.As(err, &target)
+	if !ok {
+		t.Error("Expected an InvalidAddrError")
+	}
+}
+
 // TestGetLDAPErrorSuccess tests parsing of a result with no error (resultCode == 0).
 func TestGetLDAPErrorSuccess(t *testing.T) {
 	bindResponse := ber.Encode(ber.ClassApplication, ber.TypeConstructed, ApplicationBindResponse, nil, "Bind Response")