diff --git a/cli/cli.go b/cli/cli.go
index 033a594..045f8df 100644
--- a/cli/cli.go
+++ b/cli/cli.go
@@ -142,8 +142,9 @@ func (c *CLI) unmarshalRequest(request plugin.Request) error {
 
 	if err := request.Validate(); err != nil {
 		c.logger.Errorf("%s validation error :%v", reflect.TypeOf(request), err)
-		if e, ok := err.(*plugin.Error); ok {
-			return plugin.NewValidationErrorf("%s: %s", plugin.ErrorMsgMalformedInput, e.Message)
+		var plError *plugin.Error
+		if errors.As(err, &plError) {
+			return plugin.NewValidationErrorf("%s: %s", plugin.ErrorMsgMalformedInput, plError.Message)
 		}
 		return plugin.NewValidationErrorf("%s", plugin.ErrorMsgMalformedInput)
 	}
diff --git a/plugin/errors.go b/plugin/errors.go
index 6e6297f..575a257 100644
--- a/plugin/errors.go
+++ b/plugin/errors.go
@@ -34,8 +34,7 @@ const (
 	ErrorMsgMalformedOutputFmt string = "Failed to generate response. Error: %s"
 )
 
-// Error is used when the signature associated is no longer
-// valid.
+// Error is used to return a well-formed error response as per NotaryProject specification.
 type Error struct {
 	ErrCode  ErrorCode         `json:"errorCode"`
 	Message  string            `json:"errorMessage,omitempty"`