diff --git a/builder.go b/builder.go
index 2d14067..4e38818 100644
--- a/builder.go
+++ b/builder.go
@@ -29,7 +29,7 @@ func (b *Builder) AddType(t datatype.T) {
 		b.conf = &config.Server{}
 	}
 	if b.conf.Services != nil {
-		panic(ErrLateType)
+		panic(errLateType)
 	}
 	b.conf.Types = append(b.conf.Types, t)
 }
@@ -41,7 +41,7 @@ func (b *Builder) Setup(r io.Reader) error {
 		b.conf = &config.Server{}
 	}
 	if b.conf.Services != nil {
-		panic(ErrAlreadySetup)
+		panic(errAlreadySetup)
 	}
 	return b.conf.Parse(r)
 }
@@ -49,7 +49,7 @@ func (b *Builder) Setup(r io.Reader) error {
 // Bind a dynamic handler to a REST service
 func (b *Builder) Bind(method, path string, fn interface{}) error {
 	if b.conf.Services == nil {
-		return ErrNotSetup
+		return errNotSetup
 	}
 
 	// find associated service
@@ -62,7 +62,7 @@ func (b *Builder) Bind(method, path string, fn interface{}) error {
 	}
 
 	if service == nil {
-		return fmt.Errorf("%s '%s': %w", method, path, ErrUnknownService)
+		return fmt.Errorf("%s '%s': %w", method, path, errUnknownService)
 	}
 
 	dyn, err := dynfunc.Build(fn, *service)
@@ -91,7 +91,7 @@ func (b Builder) Build() (http.Handler, error) {
 			}
 		}
 		if !hasAssociatedHandler {
-			return nil, fmt.Errorf("%s '%s': %w", service.Method, service.Pattern, ErrMissingHandler)
+			return nil, fmt.Errorf("%s '%s': %w", service.Method, service.Pattern, errMissingHandler)
 		}
 	}
 
diff --git a/errors.go b/errors.go
index f3c7145..bb863b7 100644
--- a/errors.go
+++ b/errors.go
@@ -3,22 +3,21 @@ package aicra
 // cerr allows you to create constant "const" error with type boxing.
 type cerr string
 
-// Error implements the error builtin interface.
 func (err cerr) Error() string {
 	return string(err)
 }
 
-// ErrLateType - cannot add datatype after setting up the definition
-const ErrLateType = cerr("types cannot be added after Setup")
+// errLateType - cannot add datatype after setting up the definition
+const errLateType = cerr("types cannot be added after Setup")
 
-// ErrNotSetup - not set up yet
-const ErrNotSetup = cerr("not set up")
+// errNotSetup - not set up yet
+const errNotSetup = cerr("not set up")
 
-// ErrAlreadySetup - already set up
-const ErrAlreadySetup = cerr("already set up")
+// errAlreadySetup - already set up
+const errAlreadySetup = cerr("already set up")
 
-// ErrUnknownService - no service matching this handler
-const ErrUnknownService = cerr("unknown service")
+// errUnknownService - no service matching this handler
+const errUnknownService = cerr("unknown service")
 
-// ErrMissingHandler - missing handler
-const ErrMissingHandler = cerr("missing handler")
+// errMissingHandler - missing handler
+const errMissingHandler = cerr("missing handler")