diff --git a/README.md b/README.md
index 1abde3b..a772f38 100644
--- a/README.md
+++ b/README.md
@@ -25,7 +25,7 @@ Here are the timings (in seconds) for computing the Boolean intersection between
 |-------------------|-----------------------:|--------------------------:|---------------:|--------------:|-----------------------:|---------------:|
 | **Open**          |                    4.6 |                    FAILED |            2.8 |           1.7 |                 FAILED |         FAILED |
 | **Open & closed** |                 FAILED |                      70.5 |            2.0 |           1.3 |                 FAILED |         FAILED |
-| **Closed**        |                   57.4 |                    FAILED |            6.4 |           3.5 |                    8.9 |            1.7 |
+| **Closed**        |                   57.4 |                    FAILED |            6.4 |           3.4 |                    8.9 |            1.7 |
 | **Non-manifold**  |                 FAILED |                    FAILED |            0.5 |           0.3 |                 FAILED |         FAILED |
 
 ¹ Ran with `KIGUMI_NUM_THREADS=1`. ² Configured with `-DMANIFOLD_PAR=TBB`.
diff --git a/include/kigumi/Find_coplanar_faces.h b/include/kigumi/Find_coplanar_faces.h
index 450be31..0e82360 100644
--- a/include/kigumi/Find_coplanar_faces.h
+++ b/include/kigumi/Find_coplanar_faces.h
@@ -3,6 +3,7 @@
 #include <kigumi/Face_tag.h>
 #include <kigumi/Mesh_indices.h>
 #include <kigumi/Triangle_soup.h>
+#include <kigumi/parallel_do.h>
 
 #include <algorithm>
 #include <array>
@@ -43,14 +44,14 @@ class Find_coplanar_faces {
       triangle_to_fi.emplace(tri, fi);
     }
 
-    for (auto fi : b.faces()) {
+    parallel_do(b.faces().begin(), b.faces().end(), [&](Face_index fi) {
       auto tri = triangle(b, fi, b_points);
 
       auto it = triangle_to_fi.find(tri);
       if (it != triangle_to_fi.end()) {
         a_face_tags.at(it->second.idx()) = Face_tag::COPLANAR;
         b_face_tags.at(fi.idx()) = Face_tag::COPLANAR;
-        continue;
+        return;
       }
 
       it = triangle_to_fi.find(opposite(tri));
@@ -58,7 +59,7 @@ class Find_coplanar_faces {
         a_face_tags.at(it->second.idx()) = Face_tag::OPPOSITE;
         b_face_tags.at(fi.idx()) = Face_tag::OPPOSITE;
       }
-    }
+    });
 
     return {std::move(left_face_tags), std::move(right_face_tags)};
   }