#3 Error when clipping polygon

[Anonymous]

I have two polygons that share a single point:
+--+
| |
+--+--+
| |
+--+

Here are the points:
(-75.6679566, 39.6222665)
(-75.6611617, 39.6222373)
(-75.6611617, 39.6277492)
(-75.6679944, 39.6277492)
And
(-75.6747515, 39.6222373)
(-75.6679566, 39.6222665)
(-75.6679944, 39.6167546)
(-75.6747515, 39.6167254)

When I clip, I get an assertion:
poly.cc:208: Orientation Poly::orientation() const: Assertion `(area * tot_angle > 0) || (fabs(fabs(tot_angle) - 3.14159265358979323846 * 2.0) > 0.0001)' failed.

The part that surprises me is right before that I see this :
This should not happen! nclip.cc 220

(your line numbers may vary).

I have no idea why this happening after calling clip_poly. I certainly didn't expect the assertion failure.