diff --git a/column.go b/column.go
index 0f68809..1546927 100644
--- a/column.go
+++ b/column.go
@@ -423,5 +423,8 @@ func (c *SBaseCompoundColumn) ConvertFromValue(val interface{}) interface{} {
 	if ok && bVal != nil {
 		return bVal.String()
 	}
+	if _, ok := val.(string); ok {
+		return val
+	}
 	return jsonutils.Marshal(val).String()
 }