diff --git a/errors.go b/errors.go
index ff11b66b..5d32c137 100644
--- a/errors.go
+++ b/errors.go
@@ -10,7 +10,6 @@ type notExistErrorMessageType int
 
 const (
 	flagNotExistMessage notExistErrorMessageType = iota
-	flagNotDefinedMessage
 	flagNoSuchFlagMessage
 	flagUnknownFlagMessage
 	flagUnknownShorthandFlagMessage
@@ -30,9 +29,6 @@ func (e *NotExistError) Error() string {
 	case flagNotExistMessage:
 		return fmt.Sprintf("flag %q does not exist", e.name)
 
-	case flagNotDefinedMessage:
-		return fmt.Sprintf("flag accessed but not defined: %s", e.name)
-
 	case flagNoSuchFlagMessage:
 		return fmt.Sprintf("no such flag -%v", e.name)
 
diff --git a/flag.go b/flag.go
index 1cb047a9..c7ab867f 100644
--- a/flag.go
+++ b/flag.go
@@ -404,7 +404,7 @@ func (f *FlagSet) lookup(name NormalizedName) *Flag {
 func (f *FlagSet) getFlagType(name string, ftype string, convFunc func(sval string) (interface{}, error)) (interface{}, error) {
 	flag := f.Lookup(name)
 	if flag == nil {
-		err := &NotExistError{name: name, messageType: flagNotDefinedMessage}
+		err := &NotExistError{name: name, messageType: flagNotExistMessage}
 		return nil, err
 	}