diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8c77cec..ae6a3b0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,7 +8,7 @@ include( CheckCXXCompilerFlag )
 
 project( ZDRay )
 
-SET( CMAKE_CXX_STANDARD 14 )
+SET( CMAKE_CXX_STANDARD 17 )
 
 IF( NOT CMAKE_BUILD_TYPE )
 	SET( CMAKE_BUILD_TYPE Debug CACHE STRING
diff --git a/src/level/doomdata.h b/src/level/doomdata.h
index 1b46399..a39518e 100644
--- a/src/level/doomdata.h
+++ b/src/level/doomdata.h
@@ -7,6 +7,7 @@
 #include "math/mathlib.h"
 #include <memory>
 #include <cmath>
+#include <optional>
 #undef MIN
 #undef MAX
 #undef min
@@ -346,15 +347,15 @@ struct ThingLight
 	MapSubsectorEx  *ssect;
 
 	// Portal related functionality
-	vec3 relativePosition = vec3(0);
+	std::optional<vec3> relativePosition;
 	int sectorGroup = 0;
 
 	// Portal aware position
 	vec3 LightRelativeOrigin() const
 	{
-		if (relativePosition != vec3(0))
+		if (relativePosition)
 		{
-			return relativePosition;
+			return *relativePosition;
 		}
 		return LightOrigin();
 	}
diff --git a/src/lightmap/levelmesh.cpp b/src/lightmap/levelmesh.cpp
index 762975a..7372f63 100644
--- a/src/lightmap/levelmesh.cpp
+++ b/src/lightmap/levelmesh.cpp
@@ -205,7 +205,7 @@ void LevelMesh::PropagateLight(FLevel& doomMap, ThingLight *light)
 				{
 					auto fakeLight = std::make_unique<ThingLight>(*light);
 
-					fakeLight->relativePosition = portal->TransformPosition(light->LightRelativeOrigin());
+					fakeLight->relativePosition.emplace(portal->TransformPosition(light->LightRelativeOrigin()));
 					fakeLight->sectorGroup = portal->targetSectorGroup;
 
 					PropagateLight(doomMap, fakeLight.get());