diff --git a/DLD154Tool/main.py b/DLD154Tool/main.py
index ae2e9b9..43b58f9 100644
--- a/DLD154Tool/main.py
+++ b/DLD154Tool/main.py
@@ -276,7 +276,7 @@ class Tab700BS(QWidget):
         vl = QVBoxLayout(gb_disp)
         self._txt_disp = QTextBrowser()
         self._txt_disp.setReadOnly(True)
-        self._txt_disp.setMaximumBlockCount(200)
+        self._txt_disp.document().setMaximumBlockCount(200)
         vl.addWidget(self._txt_disp)
         layout.addWidget(gb_disp, 1)
 
@@ -416,7 +416,7 @@ class TabModbus(QWidget):
         vl = QVBoxLayout(gb_disp)
         self._txt_modbus = QTextBrowser()
         self._txt_modbus.setReadOnly(True)
-        self._txt_modbus.setMaximumBlockCount(500)
+        self._txt_modbus.document().setMaximumBlockCount(500)
         self._txt_modbus.setFontFamily("monospace")
         vl.addWidget(self._txt_modbus)
         layout.addWidget(gb_disp, 1)
@@ -517,7 +517,7 @@ class LogTab(QWidget):
         layout = QVBoxLayout(self)
         self._txt_log = QTextBrowser()
         self._txt_log.setReadOnly(True)
-        self._txt_log.setMaximumBlockCount(1000)
+        self._txt_log.document().setMaximumBlockCount(1000)
         self._txt_log.setFontFamily("monospace")
         layout.addWidget(self._txt_log)