diff --git a/EasyReflectometryApp/Backends/Py/logic/layers.py b/EasyReflectometryApp/Backends/Py/logic/layers.py
index 2168e4a..4b37bfc 100644
--- a/EasyReflectometryApp/Backends/Py/logic/layers.py
+++ b/EasyReflectometryApp/Backends/Py/logic/layers.py
@@ -3,6 +3,7 @@
 from easyreflectometry import Project as ProjectLib
 from easyreflectometry.sample import LayerAreaPerMolecule
 from easyreflectometry.sample import LayerCollection
+from easyreflectometry.sample import Material
 
 
 class Layers:
@@ -42,7 +43,7 @@ def remove_at_index(self, value: str) -> None:
 
     def add_new(self) -> None:
         if 'Si' not in [material.name for material in self._project_lib._materials]:
-            self._project_lib._materials.add_material('Si', 2.07, 0.0)
+            self._project_lib._materials.add_material(Material(name='Si', sld=2.07, isld=0.0))
         index_si = [material.name for material in self._project_lib._materials].index('Si')
         self._layers.add_layer()
         self._layers[-1].material = self._project_lib._materials[index_si]
diff --git a/EasyReflectometryApp/Backends/Py/sample.py b/EasyReflectometryApp/Backends/Py/sample.py
index 96e6c7a..1bb3dd2 100644
--- a/EasyReflectometryApp/Backends/Py/sample.py
+++ b/EasyReflectometryApp/Backends/Py/sample.py
@@ -145,7 +145,6 @@ def setCurrentModelIndex(self, new_value: int) -> None:
         self._project_lib.current_model_index = new_value
         self.modelsIndexChanged.emit()
         self.assembliesTableChanged.emit()
-        self._clearCacheAndEmitLayersChanged()
         self.externalRefreshPlot.emit()
 
     @Slot(str)
diff --git a/pyproject.toml b/pyproject.toml
index 424a5a8..7ac6ad5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -41,7 +41,8 @@ dependencies = [
 ci = [
   'pyinstaller',
   'licensename',
-  'dephell_licenses'
+  'dephell_licenses',
+  'charset-normalizer<3.2',
 ]
 
 docs = [