diff --git a/FoldOptLib/FoldModellingPlugin/__init__.py b/FoldOptLib/FoldModellingPlugin/__init__.py
new file mode 100644
index 0000000..de4ba85
--- /dev/null
+++ b/FoldOptLib/FoldModellingPlugin/__init__.py
@@ -0,0 +1,20 @@
+"""Compatibility layer exposing FoldOptLib modules under the
+``FoldModellingPlugin`` namespace used by the tests."""
+from importlib import import_module
+import sys
+
+_modules = {
+    'fold_modelling': 'FoldOptLib.fold_modelling',
+    'helper': 'FoldOptLib.helper',
+    'optimisers': 'FoldOptLib.optimisers',
+    'objective_functions': 'FoldOptLib.objective_functions',
+    'splot': 'FoldOptLib.splot',
+    'input': 'FoldOptLib.input',
+    'from_loopstructural': 'FoldOptLib.from_loopstructural',
+}
+
+for name, target in _modules.items():
+    module = import_module(target)
+    setattr(sys.modules[__name__], name, module)
+    sys.modules[f'{__name__}.{name}'] = module
+
diff --git a/FoldOptLib/fold_modelling_plugin/__init__.py b/FoldOptLib/fold_modelling_plugin/__init__.py
new file mode 100644
index 0000000..de4ba85
--- /dev/null
+++ b/FoldOptLib/fold_modelling_plugin/__init__.py
@@ -0,0 +1,20 @@
+"""Compatibility layer exposing FoldOptLib modules under the
+``FoldModellingPlugin`` namespace used by the tests."""
+from importlib import import_module
+import sys
+
+_modules = {
+    'fold_modelling': 'FoldOptLib.fold_modelling',
+    'helper': 'FoldOptLib.helper',
+    'optimisers': 'FoldOptLib.optimisers',
+    'objective_functions': 'FoldOptLib.objective_functions',
+    'splot': 'FoldOptLib.splot',
+    'input': 'FoldOptLib.input',
+    'from_loopstructural': 'FoldOptLib.from_loopstructural',
+}
+
+for name, target in _modules.items():
+    module = import_module(target)
+    setattr(sys.modules[__name__], name, module)
+    sys.modules[f'{__name__}.{name}'] = module
+
diff --git a/FoldOptLib/from_loopstructural/_fold_frame.py b/FoldOptLib/from_loopstructural/_fold_frame.py
index a2edd81..2ba09bf 100644
--- a/FoldOptLib/from_loopstructural/_fold_frame.py
+++ b/FoldOptLib/from_loopstructural/_fold_frame.py
@@ -154,7 +154,7 @@ def calculate_intersection_lineation(self, points, gradient):
         """
         points = np.vstack(points)
         s1g = self.features[0].evaluate_gradient(points)
-        s1g /= np.linalg.norm(points, axis=1)[:, None]
+        s1g /= np.linalg.norm(s1g, axis=1)[:, None]
         gradient /= np.linalg.norm(gradient, axis=1)[:, None]
         l1 = np.cross(s1g, gradient)
         l1 /= np.linalg.norm(l1, axis=1)[:, None]