diff --git a/python/pyplugin_installer/installer_data.py b/python/pyplugin_installer/installer_data.py
index 9064026bdbd..d6136f59619 100644
--- a/python/pyplugin_installer/installer_data.py
+++ b/python/pyplugin_installer/installer_data.py
@@ -41,7 +41,7 @@ try:
 except ImportError:
     from imp import reload
 import qgis.utils
-from qgis.core import Qgis, QgsNetworkAccessManager, QgsAuthManager
+from qgis.core import Qgis, QgsNetworkAccessManager, QgsApplication
 from qgis.gui import QgsMessageBar
 from qgis.utils import iface, plugin_paths
 from .version_compare import compareVersions, normalizeVersion, isCompatible
@@ -333,7 +333,7 @@ class Repositories(QObject):
         self.mRepositories[key]["QRequest"] = QNetworkRequest(url)
         authcfg = self.mRepositories[key]["authcfg"]
         if authcfg and isinstance(authcfg, str):
-            if not QgsAuthManager.instance().updateNetworkRequest(
+            if not QgsApplication.authManager().updateNetworkRequest(
                     self.mRepositories[key]["QRequest"], authcfg.strip()):
                 msg = QCoreApplication.translate(
                     "QgsPluginInstaller",
diff --git a/python/pyplugin_installer/qgsplugininstallerinstallingdialog.py b/python/pyplugin_installer/qgsplugininstallerinstallingdialog.py
index fe69d6246ae..f656b8ec579 100644
--- a/python/pyplugin_installer/qgsplugininstallerinstallingdialog.py
+++ b/python/pyplugin_installer/qgsplugininstallerinstallingdialog.py
@@ -30,7 +30,7 @@ from qgis.PyQt.QtWidgets import QDialog
 from qgis.PyQt.QtNetwork import QNetworkRequest, QNetworkReply
 
 import qgis
-from qgis.core import QgsNetworkAccessManager, QgsAuthManager
+from qgis.core import QgsNetworkAccessManager, QgsApplication
 
 from .ui_qgsplugininstallerinstallingbase import Ui_QgsPluginInstallerInstallingDialogBase
 from .installer_data import removeDir, repositories
@@ -60,7 +60,7 @@ class QgsPluginInstallerInstallingDialog(QDialog, Ui_QgsPluginInstallerInstallin
         self.request = QNetworkRequest(url)
         authcfg = repositories.all()[plugin["zip_repository"]]["authcfg"]
         if authcfg and isinstance(authcfg, str):
-            if not QgsAuthManager.instance().updateNetworkRequest(
+            if not QgsApplication.authManager().updateNetworkRequest(
                     self.request, authcfg.strip()):
                 self.mResult = self.tr(
                     "Update of network request with authentication "