diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index 1d8c5c0a4..e972d909c 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -3,6 +3,7 @@ D1X-Rebirth Changelog
 20100717
 --------
 main/gamesave.c, main/render.c: Removed OGL hack to fix overlapping room in D1 lvl19 and rather move vertex a little. Still a hack but now without messing Depth test
+main/gameseg.c, main/render.c: Instead of screwing by possibly using negative array indicies in find_seg_side() return -1. In ordering segments make this result in unimportant order; Taking in some Asserts which were disabled years ago by me. Let's fix this for real when we get to it
 
 20100716
 --------
diff --git a/main/gameseg.c b/main/gameseg.c
index 0a5d62085..35b8684ba 100644
--- a/main/gameseg.c
+++ b/main/gameseg.c
@@ -305,7 +305,7 @@ segmasks get_seg_masks(vms_vector *checkp,int segnum,fix rad,char *calling_file,
 	int			vertex_list[6];
 	segment		*seg;
 
-// 	Assert((segnum <= Highest_segment_index) && (segnum >= 0)); // ZICO - FIXME
+	Assert((segnum <= Highest_segment_index) && (segnum >= 0));
 
 	seg = &Segments[segnum];
 
diff --git a/main/render.c b/main/render.c
index 7b5af338f..199d6ac98 100644
--- a/main/render.c
+++ b/main/render.c
@@ -923,7 +923,8 @@ int find_seg_side(segment *seg,short *verts,int notside)
 		}
 	}
 
-// 	Assert(vv0!=-1 && vv1!=-1); // ZICO - disabled. will fail sometimes in some 4D levels.
+	if (vv0 == -1 || vv1 != -1)
+		return -1;
 
 	eptr = Edge_to_sides[vv0][vv1];
 
@@ -967,7 +968,9 @@ int find_joining_side_norms(vms_vector *norm0_0,vms_vector *norm0_1,vms_vector *
 	Assert(notside1 != -1);
 
 	edgeside0 = find_seg_side(seg0,edge_verts,notside0);
+	if (edgeside0 == -1) return 0;
 	edgeside1 = find_seg_side(seg1,edge_verts,notside1);
+	if (edgeside1 == -1) return 0;
 
 	//deal with the case where an edge is shared by more than two segments
 
@@ -1040,8 +1043,8 @@ int compare_children(segment *seg,short c0,short c1)
 
 	t = find_joining_side_norms(&norm0_0,&norm0_1,&norm1_0,&norm1_1,&pnt0,&pnt1,seg,c0,c1);
 
-//if (!t)
-// return 0;
+	if (!t) // can happen - 4D rooms!
+		return 0;
 
 	vm_vec_sub(&temp,&Viewer_eye,pnt0);
 	d0_0 = vm_vec_dot(&norm0_0,&temp);