diff --git a/phosphor-regulators/src/id_map.hpp b/phosphor-regulators/src/id_map.hpp
index 289c7a9..c466f23 100644
--- a/phosphor-regulators/src/id_map.hpp
+++ b/phosphor-regulators/src/id_map.hpp
@@ -47,6 +47,8 @@
     /**
      * Adds the specified device to this IDMap.
      *
+     * Throws invalid_argument if the device's ID already exists in the map.
+     *
      * @param device device to add
      */
     void addDevice(Device& device);
@@ -54,6 +56,8 @@
     /**
      * Adds the specified rail to this IDMap.
      *
+     * Throws invalid_argument if the rail's ID already exists in the map.
+     *
      * @param rail rail to add
      */
     void addRail(Rail& rail);
@@ -61,6 +65,8 @@
     /**
      * Adds the specified rule to this IDMap.
      *
+     * Throws invalid_argument if the rule's ID already exists in the map.
+     *
      * @param rule rule to add
      */
     void addRule(Rule& rule);