diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5de9953..5cc1820 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed point welding bug in map_mesh function.
 - Changed example_isolines to work with the new compas_viewer.
 - GA for cibuildwheel, bring back the tessagon test.
+- Fixed planarize method to handle triangles.
 
 ### Removed
 
diff --git a/src/compas_libigl/planarize.py b/src/compas_libigl/planarize.py
index c4a35d0..f607124 100644
--- a/src/compas_libigl/planarize.py
+++ b/src/compas_libigl/planarize.py
@@ -30,10 +30,24 @@ def quadmesh_planarize(M, kmax=500, maxdev=0.005):
 
     Notes
     -----
-    The input mesh should consist primarily of quad faces for best results.
-    Non-quad faces may produce unexpected results.
+    The input mesh should consist of quad and triangle faces, else ValueError is raised.
+
+
+    Raises
+    -----
+    ValueError
+        If the input mesh contains faces other than quads or triangles.
+
     """
+
     V, F = M
+
+    for f in F:
+        if len(f) == 3:
+            f.append(f[0])
+        elif len(f) != 4:
+            raise ValueError("All faces must be quads for planarization.")
+
     V = np.asarray(V, dtype=np.float64)
     F = np.asarray(F, dtype=np.int32)
     return _planarize.planarize_quads(V, F, kmax, maxdev)