diff --git a/wadsrc/static/shaders/lightmap/frag_raytrace.glsl b/wadsrc/static/shaders/lightmap/frag_raytrace.glsl
index b15b3f2ee2..1f74a437b7 100644
--- a/wadsrc/static/shaders/lightmap/frag_raytrace.glsl
+++ b/wadsrc/static/shaders/lightmap/frag_raytrace.glsl
@@ -521,7 +521,13 @@ int TraceFirstHitTriangleT(vec3 origin, float tmin, vec3 dir, float tmax, out fl
 
 		if(surface.PortalIndex == 0)
 		{
-			break;
+			int index = primitiveID * 3;
+			vec2 uv = vertices[elements[index + 0]].uv * primitiveWeights.x + vertices[elements[index + 1]].uv * primitiveWeights.y + vertices[elements[index + 2]].uv * primitiveWeights.z;
+
+			if (texture(textures[surface.TextureIndex], uv).w > 0.9)
+			{
+				break;
+			}
 		}
 
 		// Portal was hit: Apply transformation onto the ray