diff --git a/src/p_sectors.cpp b/src/p_sectors.cpp
index 1abb971b61..743b8dc3b7 100644
--- a/src/p_sectors.cpp
+++ b/src/p_sectors.cpp
@@ -2434,6 +2434,7 @@ void subsector_t::BuildPolyBSP()
 	for (unsigned int i = 0; i < BSP->Subsectors.Size(); ++i)
 	{
 		BSP->Subsectors[i].sector = sector;
+		BSP->Subsectors[i].section = section;
 	}
 }