diff --git a/src/gui_qt/fit/fitfunction.py b/src/gui_qt/fit/fitfunction.py
index 878f166..54ce567 100644
--- a/src/gui_qt/fit/fitfunction.py
+++ b/src/gui_qt/fit/fitfunction.py
@@ -235,7 +235,19 @@ class QFunctionWidget(QtWidgets.QWidget, Ui_Form):
         return all_parameters
 
     def get_complex_state(self):
-        return self.complex_comboBox.currentIndex() if self.iscomplex else None
+        iscomplex = False
+        iterator = QtWidgets.QTreeWidgetItemIterator(self.functree)
+        while iterator.value():
+            item = iterator.value()
+            if item.checkState(0) != QtCore.Qt.CheckState.Unchecked:
+                f = self.functions[item.data(0, QtCore.Qt.UserRole)]
+                if hasattr(f, 'iscomplex') and f.iscomplex:
+                    iscomplex = True
+                    break
+
+            iterator += 1
+
+        return self.complex_comboBox.currentIndex() if iscomplex else None
 
     def set_complex_state(self, state):
         if state is not None:
diff --git a/src/gui_qt/lib/codeeditor.py b/src/gui_qt/lib/codeeditor.py
index 1b80d4d..5bf0e04 100644
--- a/src/gui_qt/lib/codeeditor.py
+++ b/src/gui_qt/lib/codeeditor.py
@@ -1,5 +1,6 @@
 # CodeEditor based on QT example, Python syntax highlighter found on Python site
-
+import typing
+from ast import parse
 
 from ..Qt import QtGui, QtCore, QtWidgets
 
@@ -184,6 +185,7 @@ class CodeEditor(QtWidgets.QPlainTextEdit):
         self.update_width_linenumber(0)
 
         self.highlight = PythonHighlighter(self.document())
+        self.textChanged.connect(self._check_syntax)
 
     def keyPressEvent(self, evt):
         if evt.key() == QtCore.Qt.Key_Tab:
@@ -260,3 +262,23 @@ class CodeEditor(QtWidgets.QPlainTextEdit):
             extra_selections.append(selection)
 
         self.setExtraSelections(extra_selections)
+
+    def color_line(self, color):
+        # is_valid, exception = self._check_syntax()
+        # if is_valid == 1:
+        doc = self.document()
+        print(doc.findBlockByLineNumber(color))
+
+    def _check_syntax(self) -> (int, tuple[typing.Any]):
+        # Compile into an AST and check for syntax errors.
+        try:
+            _ = parse(self.toPlainText(), filename='<string>')
+        except SyntaxError as e:
+            print('SyntaxError', e, e.args[0], e.lineno, e.offset, e.text)
+            self.color_line(e.lineno)
+            return 1, (e.lineno, e.offset)
+        except Exception as e:
+            print('Unexpected error', e)
+            return 2, (e.args[0],)
+
+        return 0, tuple()
diff --git a/src/nmreval/fit/minimizer.py b/src/nmreval/fit/minimizer.py
index 9ed33fa..cafca40 100644
--- a/src/nmreval/fit/minimizer.py
+++ b/src/nmreval/fit/minimizer.py
@@ -227,8 +227,6 @@ class FitRoutine(object):
         if mode is None:
             mode = self.fitmethod
 
-        print('run')
-
         fit_groups, linked_parameter = self.prepare_links()
         for data_groups in fit_groups:
             if len(data_groups) == 1 and not self.linked:
@@ -236,8 +234,6 @@ class FitRoutine(object):
                 # get variable parameter for fitter
                 p0_k, lb_k, ub_k, var_pars_k = self._prep_data(data)
 
-                print(p0_k, var_pars_k)
-
                 if mode == 'lsq':
                     self._least_squares_single(data, p0_k, lb_k, ub_k, var_pars_k)
 
@@ -252,7 +248,6 @@ class FitRoutine(object):
                 data_pars, p0, lb, ub, var_pars = self._prep_global(data_groups, linked_parameter)
 
                 if mode == 'lsq':
-                    print(data_pars, p0,var_pars)
                     self._least_squares_global(data_groups, p0, lb, ub, var_pars, data_pars)
 
                 elif mode == 'nm':