diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0274dfb..41c4d9f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14,7 +14,7 @@ set(META_VERSION_MAJOR 1)
 set(META_VERSION_MINOR 5)
 set(META_VERSION_PATCH 5)
 set(META_RELEASE_DATE "2024-06-04")
-set(META_SOVERSION 15)
+set(META_SOVERSION 16)
 set(META_ADD_DEFAULT_CPP_UNIT_TEST_APPLICATION ON)
 set(NETWORK_INFORMATION_SUPPORT ON)
 
diff --git a/syncthingconnector/syncthingconnection.cpp b/syncthingconnector/syncthingconnection.cpp
index 3524bb6..20953c2 100644
--- a/syncthingconnector/syncthingconnection.cpp
+++ b/syncthingconnector/syncthingconnection.cpp
@@ -119,6 +119,7 @@ SyncthingConnection::SyncthingConnection(
 #ifdef SYNCTHINGCONNECTION_SUPPORT_METERED
     , m_handlingMeteredConnectionInitialized(false)
 #endif
+    , m_insecure(false)
 {
     m_trafficPollTimer.setInterval(SyncthingConnectionSettings::defaultTrafficPollInterval);
     m_trafficPollTimer.setTimerType(Qt::VeryCoarseTimer);
diff --git a/syncthingconnector/syncthingconnection.h b/syncthingconnector/syncthingconnection.h
index 69a729d..b76460f 100644
--- a/syncthingconnector/syncthingconnection.h
+++ b/syncthingconnector/syncthingconnection.h
@@ -160,6 +160,7 @@ class LIB_SYNCTHING_CONNECTOR_EXPORT SyncthingConnection : public QObject {
     Q_PROPERTY(QJsonObject rawConfig READ rawConfig NOTIFY newConfig)
     Q_PROPERTY(bool useDeprecatedRoutes READ isUsingDeprecatedRoutes WRITE setUseDeprecatedRoutes)
     Q_PROPERTY(bool pausingOnMeteredConnection READ isPausingOnMeteredConnection WRITE setPausingOnMeteredConnection)
+    Q_PROPERTY(bool insecure READ isInsecure WRITE setInsecure)
 
 public:
     explicit SyncthingConnection(const QString &syncthingUrl = QStringLiteral("http://localhost:8080"), const QByteArray &apiKey = QByteArray(),
@@ -220,6 +221,8 @@ public:
     void setLongPollingTimeout(int longPollingTimeout);
     bool isPausingOnMeteredConnection() const;
     void setPausingOnMeteredConnection(bool pausingOnMeteredConnection);
+    bool isInsecure() const;
+    void setInsecure(bool insecure);
 
     // getter for information retrieved from Syncthing
     const QString &configDir() const;
@@ -527,6 +530,7 @@ private:
 #ifdef SYNCTHINGCONNECTION_SUPPORT_METERED
     bool m_handlingMeteredConnectionInitialized;
 #endif
+    bool m_insecure;
 };
 
 /*!
@@ -870,6 +874,23 @@ inline bool SyncthingConnection::isPausingOnMeteredConnection() const
     return m_pausingOnMeteredConnection;
 }
 
+/*!
+ * \brief Returns whether any certificate errors will be ignored.
+ * \remarks This will only ever be the case when this has been configured via setInsecure().
+ */
+inline bool SyncthingConnection::isInsecure() const
+{
+    return m_insecure;
+}
+
+/*!
+ * \brief Sets whether any certificate errors will be ignored.
+ */
+inline void SyncthingConnection::setInsecure(bool insecure)
+{
+    m_insecure = insecure;
+}
+
 /*!
  * \brief Returns what information is considered to compute the overall status returned by status().
  */
diff --git a/syncthingconnector/syncthingconnection_requests.cpp b/syncthingconnector/syncthingconnection_requests.cpp
index d58a8e4..d6d8fa0 100644
--- a/syncthingconnector/syncthingconnection_requests.cpp
+++ b/syncthingconnector/syncthingconnection_requests.cpp
@@ -217,7 +217,7 @@ void SyncthingConnection::handleSslErrors(const QList<QSslError> &errors)
     }
 
     // proceed if all errors are expected
-    if (!hasUnexpectedErrors) {
+    if (!hasUnexpectedErrors || m_insecure) {
         reply->ignoreSslErrors();
     }
 }
diff --git a/syncthingwidgets/settings/settings.cpp b/syncthingwidgets/settings/settings.cpp
index 7e04d86..fbb1fac 100644
--- a/syncthingwidgets/settings/settings.cpp
+++ b/syncthingwidgets/settings/settings.cpp
@@ -437,6 +437,7 @@ bool restore()
     // restore developer settings from environment variables
     setVarFromEnv(v.fakeFirstLaunch, PROJECT_VARNAME_UPPER "_FAKE_FIRST_LAUNCH");
     setVarFromEnv(v.enableWipFeatures, PROJECT_VARNAME_UPPER "_ENABLE_WIP_FEATURES");
+    setVarFromEnv(v.connection.insecure, PROJECT_VARNAME_UPPER "_INSECURE");
 
     return v.error.isEmpty();
 }
diff --git a/syncthingwidgets/settings/settings.h b/syncthingwidgets/settings/settings.h
index a7990ce..abe3d71 100644
--- a/syncthingwidgets/settings/settings.h
+++ b/syncthingwidgets/settings/settings.h
@@ -46,6 +46,7 @@ namespace Settings {
 struct SYNCTHINGWIDGETS_EXPORT Connection {
     Data::SyncthingConnectionSettings primary;
     std::vector<Data::SyncthingConnectionSettings> secondary;
+    bool insecure = false; // not persistent, for testing purposes only
 
     void addConfigFromWizard(const Data::SyncthingConfig &config);
 };
diff --git a/tray/application/main.cpp b/tray/application/main.cpp
index 4e09edc..d96b20f 100644
--- a/tray/application/main.cpp
+++ b/tray/application/main.cpp
@@ -166,6 +166,8 @@ static int runApplication(int argc, const char *const *argv)
     assumeFirstLaunchArg.setFlags(Argument::Flags::Deprecated, true); // hide as it is debug-only
     auto wipArg = ConfigValueArgument("wip", '\0', "enables WIP features");
     wipArg.setFlags(Argument::Flags::Deprecated, true); // hide as it is debug-only
+    auto insecureArg = ConfigValueArgument("insecure", '\0', "allow any self-signed certificate");
+    insecureArg.setFlags(Argument::Flags::Deprecated, true); // hide as it is only for development
     auto waitForTrayArg = ConfigValueArgument("wait", '\0',
         "wait until the system tray becomes available instead of showing an error message if the system tray is not available on start-up");
     auto connectionArg = ConfigValueArgument("connection", '\0', "specifies one or more connection configurations to be used", { "config name" });
@@ -179,7 +181,7 @@ static int runApplication(int argc, const char *const *argv)
     quitArg.setFlags(Argument::Flags::Deprecated, true); // hide as only used internally for --replace
     auto &widgetsGuiArg = qtConfigArgs.qtWidgetsGuiArg();
     widgetsGuiArg.addSubArguments({ &windowedArg, &showWebUiArg, &triggerArg, &waitForTrayArg, &connectionArg, &configPathArg, &singleInstanceArg,
-        &newInstanceArg, &replaceArg, &showWizardArg, &assumeFirstLaunchArg, &wipArg });
+        &newInstanceArg, &replaceArg, &showWizardArg, &assumeFirstLaunchArg, &wipArg, &insecureArg });
 #ifdef SYNCTHINGTRAY_USE_LIBSYNCTHING
     auto cliArg = OperationArgument("cli", 'c', "runs Syncthing's CLI");
     auto cliHelp = ConfigValueArgument("help", 'h', "shows help for Syncthing's CLI");
@@ -255,6 +257,9 @@ static int runApplication(int argc, const char *const *argv)
         if (wipArg.isPresent()) {
             settings.enableWipFeatures = true;
         }
+        if (insecureArg.isPresent()) {
+            settings.connection.insecure = true;
+        }
         LOAD_QT_TRANSLATIONS;
         if (!settings.error.isEmpty()) {
             QMessageBox::critical(nullptr, QCoreApplication::applicationName(), settings.error);
diff --git a/tray/gui/traywidget.cpp b/tray/gui/traywidget.cpp
index 9d41913..29d688f 100644
--- a/tray/gui/traywidget.cpp
+++ b/tray/gui/traywidget.cpp
@@ -107,6 +107,9 @@ TrayWidget::TrayWidget(TrayMenu *parent)
         m_tabTexts << m_ui->tabWidget->tabText(i);
     }
 
+    // configure connection
+    m_connection.setInsecure(Settings::values().connection.insecure);
+
     // setup models and views
     m_ui->dirsTreeView->header()->setSortIndicator(0, Qt::AscendingOrder);
     m_ui->dirsTreeView->setModel(&m_sortFilterDirModel);