diff --git a/src/gui_qt/fit/fit_forms.py b/src/gui_qt/fit/fit_forms.py
index 60c3191..2a9c4a2 100644
--- a/src/gui_qt/fit/fit_forms.py
+++ b/src/gui_qt/fit/fit_forms.py
@@ -70,7 +70,7 @@ class FitModelTree(QtWidgets.QTreeWidget):
                 self.remove_function(item)
 
         elif evt.key() == QtCore.Qt.Key.Key_Space:
-            for item in self.treeWidget.selectedItems():
+            for item in self.selectedItems():
                 cs = item.checkState(0)
                 if cs == QtCore.Qt.CheckState.Unchecked:
                     item.setCheckState(0, QtCore.Qt.CheckState.Checked)
diff --git a/src/gui_qt/fit/fitwindow.py b/src/gui_qt/fit/fitwindow.py
index e71e2be..a5a4fd0 100644
--- a/src/gui_qt/fit/fitwindow.py
+++ b/src/gui_qt/fit/fitwindow.py
@@ -275,7 +275,7 @@ class QFitDialog(QtWidgets.QWidget, Ui_FitDialog):
 
         func_dict = {}
         for model_name, model_parameter in self.models.items():
-            func, order, param_len = ModelFactory.create_from_list(model_parameter)
+            func, order, param_len, _ = ModelFactory.create_from_list(model_parameter)
             multiple_funcs = isinstance(func, MultiModel)
             if func is None:
                 continue
@@ -387,7 +387,7 @@ class QFitDialog(QtWidgets.QWidget, Ui_FitDialog):
 
         func_dict = {}
         for k, mod in self.models.items():
-            func, order, param_len = ModelFactory.create_from_list(mod)
+            func, order, param_len, _ = ModelFactory.create_from_list(mod)
             multiple_funcs = isinstance(func, MultiModel)
 
             if k in data:
diff --git a/src/nmreval/fit/_meta.py b/src/nmreval/fit/_meta.py
index 889cc57..ea33d06 100644
--- a/src/nmreval/fit/_meta.py
+++ b/src/nmreval/fit/_meta.py
@@ -9,7 +9,13 @@ from inspect import signature, Parameter
 class ModelFactory:
 
     @staticmethod
-    def create_from_list(funcs: list, left=None, func_order=None, param_len=None, left_cnt=None):
+    def create_from_list(
+            funcs: list,
+            left=None,
+            func_order: list[int] = None,
+            param_len: list[int] = None,
+            left_cnt: int = 0,
+    ):
         if func_order is None:
             func_order = []
 
@@ -20,32 +26,50 @@ class ModelFactory:
             if not func['active']:
                 continue
 
-            func_order.append(func['cnt'])
-            param_len.append(len(func['func'].params))
-
             if func['children']:
-                right, _, _ = ModelFactory.create_from_list(func['children'], left_cnt=func['pos'],
-                                                            func_order=func_order, param_len=param_len)
-                right_cnt = None
-                right = MultiModel(func['func'], right, func['children'][0]['op'], left_idx=func['cnt'], right_idx=None)
+                f = func.copy()
+                f['children'] = []
+                right, _, _, right_cnt = ModelFactory.create_from_list(
+                    [f] + func['children'],
+                    left_cnt=func['pos'],
+                    func_order=func_order,
+                    param_len=param_len,
+                )
             else:
                 right = func['func']
                 right_cnt = func['cnt']
 
+                func_order.append(func['cnt'])
+                param_len.append(len(func['func'].params))
+
             if left is None:
                 left = right
                 left_cnt = right_cnt
             else:
-                left = MultiModel(left, right, func['op'],
-                                  left_idx=left_cnt, right_idx=right_cnt)
+                left = MultiModel(left, right, func['op'], left_idx=left_cnt, right_idx=right_cnt)
 
-        return left, func_order, param_len
+        return left, func_order, param_len, left_cnt
 
 
 class MultiModel:
-    op_repr = {operator.add: ' + ', operator.mul: ' * ', operator.sub: ' - ', operator.truediv: ' / '}
-    str_op = {'+': operator.add, '*': operator.mul, '-': operator.sub, '/': operator.truediv}
-    int_op = {0: operator.add, 1: operator.mul, 2: operator.sub, 3: operator.truediv}
+    op_repr = {
+        operator.add: ' + ',
+        operator.mul: ' * ',
+        operator.sub: ' - ',
+        operator.truediv: ' / ',
+    }
+    str_op = {
+        '+': operator.add,
+        '*': operator.mul,
+        '-': operator.sub,
+        '/': operator.truediv,
+    }
+    int_op = {
+        0: operator.add,
+        1: operator.mul,
+        2: operator.sub,
+        3: operator.truediv,
+    }
 
     def __init__(self,
                  left: Any,
@@ -69,6 +93,9 @@ class MultiModel:
         if self._op is None:
             raise ValueError('Invalid binary operator.')
 
+        if right_idx is None:
+            right_idx = left_idx + 1
+
         self.name = '('
         self.params = []
         self.bounds = []