diff --git a/bsp.h b/bsp.h
index 8a2aa6e..7c6a8f2 100644
--- a/bsp.h
+++ b/bsp.h
@@ -371,6 +371,7 @@ typedef struct World
                 }
 
                 double dot = p0.dotProduct(p1) / (m0 * m1);
+                if (dot < -1) dot = -1; if (dot > 1) dot = 1;   // Floating point rounding errors, YAY!
                 angleSum += acos(dot);
             }