diff --git a/source/gl_sky.c b/source/gl_sky.c
index 4d34fad..890d3e9 100644
--- a/source/gl_sky.c
+++ b/source/gl_sky.c
@@ -387,6 +387,21 @@ set_vertex (glpoly_t *p, vec3_t v, int face)
 	}
 }
 
+/*
+	find_cube_vertex
+
+	get the coords of the vertex common to the three specified faces of the
+	cube. NOTE: this WILL break if the three faces are do not share a
+	common vertex.
+*/
+static void
+find_cube_vertex (int face1, int face2, int face3, vec3_t v)
+{
+	v[face1 % 3] = 1024 * (1 - 2 * (face1 / 3));
+	v[face2 % 3] = 1024 * (1 - 2 * (face2 / 3));
+	v[face3 % 3] = 1024 * (1 - 2 * (face3 / 3));
+}
+
 void
 R_DrawSkyBoxPoly (glpoly_t *poly)
 {
@@ -421,18 +436,26 @@ R_DrawSkyBoxPoly (glpoly_t *poly)
 		if (face != prev_face) {
 			if (face % 3 == prev_face % 3) {
 			} else {
-				vec3_t l, t;
+				vec3_t l;
 				find_intersect (prev_face, last_v, face, v, l);
 
 				set_vertex(&box[prev_face].poly, l, prev_face);
-				if (box[prev_face].enter >= 0 && box[prev_face].leave == -1) {
+				if (box[prev_face].enter >=0 && box[prev_face].enter != face) {
+					vec3_t t;
+					find_cube_vertex (prev_face, face, box[face].enter, t);
 					set_vertex(&box[prev_face].poly, t, prev_face);
+				} else {
+					box[prev_face].enter = -1;
+					box[prev_face].leave = face;
 				}
-				box[prev_face].leave = face;
-				if (box[face].enter == -1 && box[face].leave >= 0) {
+				if (box[face].leave >=0 && box[face].leave != prev_face) {
+					vec3_t t;
+					find_cube_vertex (prev_face, face, box[face].leave, t);
 					set_vertex(&box[face].poly, t, face);
+				} else {
+					box[face].enter = prev_face;
+					box[face].leave = -1;
 				}
-				box[prev_face].leave = face;
 				set_vertex(&box[face].poly, l, face);
 			}
 		}