diff --git a/src/tree_data.h b/src/tree_data.h
index 4dbc158..4db32c1 100644
--- a/src/tree_data.h
+++ b/src/tree_data.h
@@ -125,7 +125,7 @@
     const char *value_str;           /**< string representation of value (for comparison, printing,...), always corresponds to value_type */
     lyd_val value;                   /**< node's value representation, always corresponds to schema->type.base */
     LY_DATA_TYPE _PACKED value_type; /**< type of the value in the node, mainly for union to avoid repeating of type detection */
-    uint8_t value_flags;             /**< type flags */
+    uint8_t value_flags;             /**< value type flags */
 };
 
 /**
@@ -227,10 +227,19 @@
     const char *value_str;           /**< string representation of value (for comparison, printing,...), always corresponds to value_type */
     lyd_val value;                   /**< node's value representation, always corresponds to schema->type.base */
     LY_DATA_TYPE _PACKED value_type; /**< type of the value in the node, mainly for union to avoid repeating of type detection */
-    uint8_t value_flags;             /**< type flags */
+    uint8_t value_flags;             /**< value type flags */
 };
 
 /**
+ * @brief Flags for values
+ */
+#define LY_VALUE_UNRES 0x01   /**< flag for unresolved leafref or instance-identifier,
+                                   leafref - value union is filled as if being the target node's type,
+                                   instance-identifier - value union should not be accessed */
+#define LY_VALUE_USER 0x02    /**< flag for a user type stored value */
+/* 0x80 is reserveed for internal use */
+
+/**
  * @brief Structure for data nodes defined as #LYS_ANYDATA or #LYS_ANYXML.
  *
  * Extension for ::lyd_node structure - replaces the ::lyd_node#child member by new #value member. The first five