diff --git a/src/_impl/_bijection_offset_impl.scad b/src/_impl/_bijection_offset_impl.scad
index e59ce4c1..873a0209 100644
--- a/src/_impl/_bijection_offset_impl.scad
+++ b/src/_impl/_bijection_offset_impl.scad
@@ -47,10 +47,11 @@ function _bijection_offset_impl(pts, d, epsilon) =
             let(
                 this_edge = offset_es[i],
                 next_edge = offset_es[i + 1],
-                p = __line_intersection2(this_edge, next_edge, epsilon)
+                p = __line_intersection2(this_edge, next_edge, epsilon),
+                // p == p to avoid [nan, nan], because [nan, nan] != [nan, nan],
+                _ = assert(p != [] && p == p, "bijection_offset failed. Parallel or conincident edges found")
             )
-            // p == p to avoid [nan, nan], because [nan, nan] != [nan, nan]
-            if(p != [] && p == p) p
+            p
         ]
     );
     
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