diff --git a/skin.scad b/skin.scad
index 98d8b21..acd00fd 100644
--- a/skin.scad
+++ b/skin.scad
@@ -96,10 +96,12 @@ function skin(profiles, closed=false, caps=true, matching="distance") =
 				cp1 = mean(prof1),
 				cp2 = mean(prof2),
 				midpt = (cp1+cp2)/2,
-				n = normalize(cp2-cp1),
 				n1 = plane_normal(plane_from_pointslist(prof1)),
 				n2 = plane_normal(plane_from_pointslist(prof2)),
-				perp = vector_angle(n1,n2)>0.01? vector_axis(n1,n2) : vector_angle(n,UP)>44? vector_axis(n,UP) : vector_axis(n,LEFT),
+				vang = vector_angle(n1,n2),
+				perp = vang>0.01 && vang<179.99? vector_axis(n1,n2) :
+					vector_angle(n1,UP)>44? vector_axis(n1,UP) :
+					vector_axis(n1,LEFT),
 				perp1 = vector_axis(n1,perp),
 				perp2 = vector_axis(n2,perp),
 				poly1 = ccw_polygon(project_plane(prof1, cp1, cp1+perp, cp1+perp1)),
diff --git a/tests/test_skin.scad b/tests/test_skin.scad
new file mode 100644
index 0000000..ecc7849
--- /dev/null
+++ b/tests/test_skin.scad
@@ -0,0 +1,19 @@
+include <BOSL2/std.scad>
+include <BOSL2/skin.scad>
+
+
+module test_skin() {
+	profiles = [
+		[[-100,-100,0], [0,100,0], [100,-100,0]],
+		[[-100,-100,100], [-100,100,100], [100,100,100], [100,-100,100]],
+	];
+	vnf1 = skin(profiles, caps=false, matching="distance");
+	assert(vnf1 == [[[-100,-100,0],[-100,100,100],[-100,-100,100],[0,100,0],[100,100,100],[100,-100,0],[100,-100,100]],[[0,1,2],[0,3,1],[3,4,1],[3,5,4],[5,6,4],[5,2,6],[5,0,2]]]);
+	vnf2 = skin(profiles, caps=true, matching="distance");
+	assert(vnf2 == [[[-100,-100,0],[-100,100,100],[-100,-100,100],[0,100,0],[100,100,100],[100,-100,0],[100,-100,100],[100,-100,0],[0,100,0],[-100,-100,0],[-100,-100,100],[-100,100,100],[100,100,100],[100,-100,100]],[[0,1,2],[0,3,1],[3,4,1],[3,5,4],[5,6,4],[5,2,6],[5,0,2],[7,8,9],[10,11,12],[12,13,10]]]);
+	vnf_polyhedron(vnf2);
+}
+test_skin();
+
+
+// vim: noexpandtab tabstop=4 shiftwidth=4 softtabstop=4 nowrap
diff --git a/version.scad b/version.scad
index bf2fa80..cf05edb 100644
--- a/version.scad
+++ b/version.scad
@@ -8,7 +8,7 @@
 //////////////////////////////////////////////////////////////////////
 
 
-BOSL_VERSION = [2,0,15];
+BOSL_VERSION = [2,0,16];
 
 
 // Section: BOSL Library Version Functions