diff --git a/pkg.go b/pkg.go
index eec7144..63ad339 100644
--- a/pkg.go
+++ b/pkg.go
@@ -9,9 +9,10 @@ import (
 
 type Error struct {
 	Wrapped error
+	ErrStr  string // wrapped error isn't necessarily json encodable
 	File    string
 	Line    int
-	Data    interface{}
+	Data    interface{} `json:",omitempty"`
 }
 
 type LogCallback func(Error)
@@ -57,9 +58,9 @@ func create(err error, data interface{}) error {
 
 	_, file, line, _ := runtime.Caller(2)
 	file = file[baseDirLength+1:]
-
 	wrapped := Error{
 		Wrapped: err,
+		ErrStr:  err.Error(),
 		File:    file,
 		Line:    line,
 		Data:    data,
@@ -71,7 +72,7 @@ func create(err error, data interface{}) error {
 
 // Wrap wraps an existing error with file and line.
 func Wrap(err error) error {
-	return create(err, "")
+	return create(err, nil)
 }
 
 func WrapData(err error, data interface{}) error {