diff --git a/src/slic3r/Utils/MacDarkMode.mm b/src/slic3r/Utils/MacDarkMode.mm
index 17f6f81287..8181abd41f 100644
--- a/src/slic3r/Utils/MacDarkMode.mm
+++ b/src/slic3r/Utils/MacDarkMode.mm
@@ -39,6 +39,7 @@ using Slic3r::GUI::unique_plugin_download_path;
 - (void)removeDownloadDelegate:(id)delegate;
 @end
 
+API_AVAILABLE(macos(11.3))
 @interface OrcaWKDownloadDelegate : NSObject <WKDownloadDelegate>
 {
     OrcaWKDownloadContext* m_context;
@@ -169,10 +170,14 @@ static void wk_decide_navigation_response(WKWebView* webView,
         should_download = should_download ||
             [disposition rangeOfString:@"attachment" options:NSCaseInsensitiveSearch].location != NSNotFound;
     }
-    decisionHandler(should_download ? WKNavigationResponsePolicyDownload : WKNavigationResponsePolicyAllow);
+    if (@available(macOS 11.3, *)) {
+        decisionHandler(should_download ? WKNavigationResponsePolicyDownload : WKNavigationResponsePolicyAllow);
+    } else {
+        decisionHandler(WKNavigationResponsePolicyAllow);
+    }
 }
 
-static void wk_did_become_download(WKWebView* webView, WKNavigationResponse*, WKDownload* download)
+static void wk_did_become_download(WKWebView* webView, WKNavigationResponse*, WKDownload* download) API_AVAILABLE(macos(11.3))
 {
     OrcaWKDownloadContext* context = wk_download_context(webView);
     if (!context)
@@ -197,7 +202,7 @@ static void wk_did_become_download_imp(id,
                                        SEL,
                                        WKWebView* webView,
                                        WKNavigationResponse* response,
-                                       WKDownload* download)
+                                       WKDownload* download) API_AVAILABLE(macos(11.3))
 {
     wk_did_become_download(webView, response, download);
 }
@@ -206,7 +211,7 @@ static void wk_did_become_action_download_imp(id,
                                               SEL,
                                               WKWebView* webView,
                                               WKNavigationAction* action,
-                                              WKDownload* download)
+                                              WKDownload* download) API_AVAILABLE(macos(11.3))
 {
     (void)action;
     OrcaWKDownloadContext* context = wk_download_context(webView);
@@ -229,14 +234,16 @@ static void install_wk_download_delegate_methods(WKWebView* webView)
                     @selector(webView:decidePolicyForNavigationResponse:decisionHandler:),
                     (IMP)wk_decide_navigation_response_imp,
                     "v@:@@@");
-    class_addMethod(delegateClass,
-                    @selector(webView:navigationResponse:didBecomeDownload:),
-                    (IMP)wk_did_become_download_imp,
-                    "v@:@@@");
-    class_addMethod(delegateClass,
-                    @selector(webView:navigationAction:didBecomeDownload:),
-                    (IMP)wk_did_become_action_download_imp,
-                    "v@:@@@");
+    if (@available(macOS 11.3, *)) {
+        class_addMethod(delegateClass,
+                        @selector(webView:navigationResponse:didBecomeDownload:),
+                        (IMP)wk_did_become_download_imp,
+                        "v@:@@@");
+        class_addMethod(delegateClass,
+                        @selector(webView:navigationAction:didBecomeDownload:),
+                        (IMP)wk_did_become_action_download_imp,
+                        "v@:@@@");
+    }
 }
 
 @implementation MacDarkMode
diff --git a/tests/slic3rutils/test_plugin_cloud_metadata.cpp b/tests/slic3rutils/test_plugin_cloud_metadata.cpp
index c34b596ee0..1232c90e60 100644
--- a/tests/slic3rutils/test_plugin_cloud_metadata.cpp
+++ b/tests/slic3rutils/test_plugin_cloud_metadata.cpp
@@ -7,6 +7,7 @@
 #include <slic3r/plugin/PluginManager.hpp>
 #include <slic3r/plugin/PythonInterpreter.hpp>
 #include <slic3r/plugin/PythonPluginInterface.hpp>
+#include <slic3r/Utils/OrcaCloudServiceAgent.hpp>
 
 #include "plugin_test_utils.hpp"
 
@@ -180,7 +181,18 @@ TEST_CASE("cloud metadata refresh preserves a plugin's stored config", "[PluginC
     CHECK_FALSE(orphaned.has_error());
     CHECK(orphaned.get_update_status() == PluginUpdateStatus::Normal);
 
-    // Orphaned is informational only: the local package must remain loadable and usable.
+    // Orphaned is informational only: the local package must remain loadable and usable. Loading
+    // it exercises get_storage_dir(), which for a cloud plugin needs a real logged-in session
+    // (PluginManager::get_storage_dir() throws otherwise) -- the same session a real user would
+    // already hold for a plugin they'd previously subscribed to and downloaded. Give the manager
+    // one via the real agent: OrcaCloudServiceAgent's constructor does no networking, and
+    // set_user_session(..., persist=false) only sets in-memory session state, so this stays a
+    // fast, offline unit test.
+    auto cloud_agent = std::make_shared<OrcaCloudServiceAgent>(get_orca_plugins_dir());
+    cloud_agent->set_user_session(/*token=*/"test-token", /*user_id=*/"test-user", /*username=*/"test-user",
+                                   /*nickname=*/"", /*avatar=*/"", /*refresh_token=*/"", /*persist=*/false);
+    manager.set_cloud_agent(cloud_agent);
+
     std::string load_error;
     manager.load_plugin(uuid, /*skip_deps=*/true);
     REQUIRE(manager.wait_for_plugin_load(uuid, std::chrono::seconds(120), load_error));