diff --git a/server.go b/server.go
index be4355e..f57fa43 100644
--- a/server.go
+++ b/server.go
@@ -3,7 +3,6 @@ package ssh
 import (
 	"context"
 	"errors"
-	"fmt"
 	"net"
 	"sync"
 	"time"
@@ -29,6 +28,8 @@ var DefaultChannelHandlers = map[string]ChannelHandler{
 	"session": DefaultSessionHandler,
 }
 
+var ErrPermissionDenied = errors.New("permission denied")
+
 // Server defines parameters for running an SSH server. The zero value for
 // Server is a valid configuration. When both PasswordHandler and
 // PublicKeyHandler are nil, no client authentication is performed.
@@ -136,7 +137,7 @@ func (srv *Server) config(ctx Context) *gossh.ServerConfig {
 		config.PasswordCallback = func(conn gossh.ConnMetadata, password []byte) (*gossh.Permissions, error) {
 			applyConnMetadata(ctx, conn)
 			if ok := srv.PasswordHandler(ctx, string(password)); !ok {
-				return ctx.Permissions().Permissions, fmt.Errorf("permission denied")
+				return ctx.Permissions().Permissions, ErrPermissionDenied
 			}
 			return ctx.Permissions().Permissions, nil
 		}
@@ -145,7 +146,7 @@ func (srv *Server) config(ctx Context) *gossh.ServerConfig {
 		config.PublicKeyCallback = func(conn gossh.ConnMetadata, key gossh.PublicKey) (*gossh.Permissions, error) {
 			applyConnMetadata(ctx, conn)
 			if ok := srv.PublicKeyHandler(ctx, key); !ok {
-				return ctx.Permissions().Permissions, fmt.Errorf("permission denied")
+				return ctx.Permissions().Permissions, ErrPermissionDenied
 			}
 			ctx.SetValue(ContextKeyPublicKey, key)
 			return ctx.Permissions().Permissions, nil
@@ -155,7 +156,7 @@ func (srv *Server) config(ctx Context) *gossh.ServerConfig {
 		config.KeyboardInteractiveCallback = func(conn gossh.ConnMetadata, challenger gossh.KeyboardInteractiveChallenge) (*gossh.Permissions, error) {
 			applyConnMetadata(ctx, conn)
 			if ok := srv.KeyboardInteractiveHandler(ctx, challenger); !ok {
-				return ctx.Permissions().Permissions, fmt.Errorf("permission denied")
+				return ctx.Permissions().Permissions, ErrPermissionDenied
 			}
 			return ctx.Permissions().Permissions, nil
 		}