diff --git a/src/build123d/importers.py b/src/build123d/importers.py
index 3b36d11..886592e 100644
--- a/src/build123d/importers.py
+++ b/src/build123d/importers.py
@@ -48,7 +48,6 @@ from OCP.BRepBuilderAPI import (
     BRepBuilderAPI_Sewing,
 )
 from OCP.gp import gp_Pnt
-from OCP.ShapeAnalysis import ShapeAnalysis_Shell
 
 from build123d.topology import (
     Compound,
@@ -185,16 +184,24 @@ def import_stl(file_name: str, for_reference: bool = True) -> Union[Face, Solid]
             shell_builder.Add(face)
         shell_builder.Perform()
         occ_shell = downcast(shell_builder.SewedShape())
-        shell_analyzer = ShapeAnalysis_Shell()
-        shell_analyzer.LoadShells(occ_shell)
-        is_manifold = shell_analyzer.HasFreeEdges()
+
+        # Check of the shell is open or closed
+        edge_count = {}
+        for face in Shell(occ_shell).faces():
+            for edge in face.edges():
+                if edge in edge_count:
+                    edge_count[edge] += 1
+                else:
+                    edge_count[edge] = 1
+
+        unique_edges = [edge for edge, count in edge_count.items() if count == 1]
 
         # Create a solid
-        if is_manifold:
+        if unique_edges:
+            stl_obj = Shell(occ_shell)
+        else:
             solid_builder = BRepBuilderAPI_MakeSolid(occ_shell)
             stl_obj = Solid(solid_builder.Solid())
-        else:
-            stl_obj = Shell(occ_shell)
     return stl_obj
 
 
diff --git a/tests/test_direct_api.py b/tests/test_direct_api.py
index 469f97f..b4956b0 100644
--- a/tests/test_direct_api.py
+++ b/tests/test_direct_api.py
@@ -1161,20 +1161,30 @@ class TestImportExport(DirectApiTestCase):
             step_box = import_step("test_box.step")
 
     def test_import_stl(self):
+        # import solid
         original_box = Solid.make_box(1, 2, 3)
-        original_box.export_stl("test_box.stl")
-        stl_box = import_stl("test_box.stl", for_reference=False).clean()
+        original_box.export_stl("test.stl")
+        stl_box = import_stl("test.stl", for_reference=False).clean()
         self.assertEqual(len(stl_box.vertices()), 8)
         self.assertEqual(len(stl_box.edges()), 12)
         self.assertEqual(len(stl_box.faces()), 6)
+        self.assertTrue(isinstance(stl_box, Solid))
         self.assertAlmostEqual(stl_box.volume, 1 * 2 * 3, 5)
 
-        stl_box = import_stl("test_box.stl", for_reference=True)
+        # import as face
+        stl_box = import_stl("test.stl", for_reference=True)
         self.assertVectorAlmostEquals(stl_box.position, (0, 0, 0), 5)
 
-        os.remove("test_box.stl")
+        # import shell
+        original_face = Face.make_rect(1, 2)
+        original_face.export_stl("test.stl")
+        stl_face = import_stl("test.stl", for_reference=False).clean()
+        self.assertTrue(isinstance(stl_face, Shell))
+
+        # missing file
+        os.remove("test.stl")
         with self.assertRaises(ValueError):
-            import_stl("test_box.stl", for_reference=False)
+            import_stl("test.stl", for_reference=False)
 
 
 class TestJoints(DirectApiTestCase):