diff --git a/trview.app.tests/Windows/ViewerTests.cpp b/trview.app.tests/Windows/ViewerTests.cpp
index c23b4c953..7f091815d 100644
--- a/trview.app.tests/Windows/ViewerTests.cpp
+++ b/trview.app.tests/Windows/ViewerTests.cpp
@@ -1083,6 +1083,35 @@ TEST(Viewer, SectorHighlightForwarded)
     ui.on_sector_hover(sector);
 }
 
+TEST(Viewer, AlternateGroupForwarded)
+{
+    auto level = mock_shared<MockLevel>();
+    EXPECT_CALL(*level, set_alternate_group(6, true)).Times(1);
+    ON_CALL(*level, alternate_groups).WillByDefault(Return(std::set<uint32_t>{ 6 }));
+
+    auto [ui_ptr, ui] = create_mock<MockViewerUI>();
+    EXPECT_CALL(ui, set_alternate_group(6, true)).Times(1);
+
+    auto viewer = register_test_module().with_ui(std::move(ui_ptr)).build();
+    viewer->open(level, ILevel::OpenMode::Full);
+
+    ui.on_alternate_group(6, true);
+}
+
+TEST(Viewer, InvalidAlternateGroupNotForwarded)
+{
+    auto level = mock_shared<MockLevel>();
+    EXPECT_CALL(*level, set_alternate_group).Times(0);
+
+    auto [ui_ptr, ui] = create_mock<MockViewerUI>();
+    EXPECT_CALL(ui, set_alternate_group).Times(0);
+
+    auto viewer = register_test_module().with_ui(std::move(ui_ptr)).build();
+    viewer->open(level, ILevel::OpenMode::Full);
+
+    ui.on_alternate_group(6, true);
+}
+
 TEST(Viewer, FontForwarded)
 {
     auto [ui_ptr, ui] = create_mock<MockViewerUI>();
diff --git a/trview.app/Windows/Viewer.cpp b/trview.app/Windows/Viewer.cpp
index 4301c623a..5c7c00882 100644
--- a/trview.app/Windows/Viewer.cpp
+++ b/trview.app/Windows/Viewer.cpp
@@ -961,9 +961,12 @@ namespace trview
     {
         if (auto level = _level.lock())
         {
-            _was_alternate_select = true;
-            level->set_alternate_group(group, enabled);
-            _ui->set_alternate_group(group, enabled);
+            if (std::ranges::contains(level->alternate_groups(), group))
+            {
+                _was_alternate_select = true;
+                level->set_alternate_group(group, enabled);
+                _ui->set_alternate_group(group, enabled);
+            }
         }
     }