diff --git a/src/r_main.c b/src/r_main.c
index 1ad125cd0..498f4dab8 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -771,7 +771,7 @@ subsector_t *R_PointInSubsector(fixed_t x, fixed_t y)
 }
 
 //
-// R_IsPointInSubsector, same as above but returns 0 if not in subsector
+// R_IsPointInSubsector, same as above but returns 0 if not in subsector - this does not work in opengl because of polyvertex_t
 //
 subsector_t *R_IsPointInSubsector(fixed_t x, fixed_t y)
 {