--- a/src/Mod/Sketcher/App/GeoEnum.h
+++ b/src/Mod/Sketcher/App/GeoEnum.h
@@ -114,6 +114,10 @@
      */
     bool operator==(const GeoElementId& obj) const;
 
+    /** @brief less-than operator
+     */
+    bool operator<(const GeoElementId& obj) const;
+
     /** @brief inequality operator
      */
     bool operator!=(const GeoElementId& obj) const;
--- a/src/Mod/Sketcher/App/GeoEnum.cpp
+++ b/src/Mod/Sketcher/App/GeoEnum.cpp
@@ -32,6 +32,13 @@
     return this->GeoId == obj.GeoId && this->Pos == obj.Pos;
 }
 
+bool GeoElementId::operator<(const GeoElementId& obj) const
+{
+    return (this->GeoId != obj.GeoId)
+        ? (this->GeoId < obj.GeoId)
+        : (static_cast<int>(this->Pos) < static_cast<int>(obj.Pos));
+}
+
 bool GeoElementId::operator!=(const GeoElementId& obj) const
 {
     return this->GeoId != obj.GeoId || this->Pos != obj.Pos;