Index: trunk/src/org/openstreetmap/josm/gui/preferences/server/AuthenticationPreferencesPanel.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/preferences/server/AuthenticationPreferencesPanel.java	(revision 18827)
+++ trunk/src/org/openstreetmap/josm/gui/preferences/server/AuthenticationPreferencesPanel.java	(revision 18828)
@@ -18,7 +18,9 @@
 import javax.swing.JRadioButton;
 
+import org.openstreetmap.josm.actions.ExpertToggleAction;
 import org.openstreetmap.josm.data.UserIdentityManager;
 import org.openstreetmap.josm.data.oauth.OAuthAccessTokenHolder;
 import org.openstreetmap.josm.data.oauth.OAuthVersion;
+import org.openstreetmap.josm.data.preferences.JosmUrls;
 import org.openstreetmap.josm.gui.help.HelpUtil;
 import org.openstreetmap.josm.gui.widgets.VerticallyScrollablePanel;
@@ -50,4 +52,14 @@
     private OAuthAuthenticationPreferencesPanel pnlOAuth20Preferences;
 
+    /** Used to determine which API we are using for disabling/enabling Basic Auth/OAuth 1.0a */
+    private String apiUrl = OsmApi.getOsmApi().getServerUrl();
+    /** ExpertToggleAction uses weak references; we don't want this listener to be garbage collected */
+    private final ExpertToggleAction.ExpertModeChangeListener expertModeChangeListener = isExpert -> {
+        final String authMethod = OsmApi.getAuthMethod();
+        final boolean defaultApi = JosmUrls.getInstance().getDefaultOsmApiUrl().equals(apiUrl);
+        rbBasicAuthentication.setEnabled(rbBasicAuthentication.isSelected() || "basic".equals(authMethod) || isExpert || !defaultApi);
+        rbOAuth.setEnabled(rbOAuth.isSelected() || "oauth".equals(authMethod) || isExpert || !defaultApi);
+    };
+
     /**
      * Constructs a new {@code AuthenticationPreferencesPanel}.
@@ -110,6 +122,8 @@
         pnlOAuth20Preferences = new OAuthAuthenticationPreferencesPanel(OAuthVersion.OAuth20);
 
-        rbBasicAuthentication.setSelected(true);
-        pnlAuthenticationParameters.add(pnlBasicAuthPreferences, BorderLayout.CENTER);
+        ExpertToggleAction.addExpertModeChangeListener(expertModeChangeListener, true);
+
+        rbOAuth20.setSelected(true);
+        pnlAuthenticationParameters.add(pnlOAuth20Preferences, BorderLayout.CENTER);
     }
 
@@ -178,4 +192,5 @@
             }
         }
+        ExpertToggleAction.removeExpertModeChangeListener(this.expertModeChangeListener);
     }
 
@@ -210,4 +225,11 @@
             pnlOAuthPreferences.propertyChange(evt);
         }
+        if (pnlOAuth20Preferences != null) {
+            pnlOAuth20Preferences.propertyChange(evt);
+        }
+        if (OsmApiUrlInputPanel.API_URL_PROP.equals(evt.getPropertyName())) {
+            this.apiUrl = (String) evt.getNewValue();
+            this.expertModeChangeListener.expertChanged(ExpertToggleAction.isExpert());
+        }
     }
 }
Index: trunk/test/unit/org/openstreetmap/josm/gui/io/importexport/OsmPbfImporterTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/gui/io/importexport/OsmPbfImporterTest.java	(revision 18827)
+++ trunk/test/unit/org/openstreetmap/josm/gui/io/importexport/OsmPbfImporterTest.java	(revision 18828)
@@ -19,6 +19,4 @@
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.ValueSource;
 import org.openstreetmap.josm.TestUtils;
 import org.openstreetmap.josm.data.coor.ILatLon;