diff --git a/src/moonset/main.py b/src/moonset/main.py
index cbd643d..8eeb764 100644
--- a/src/moonset/main.py
+++ b/src/moonset/main.py
@@ -2,9 +2,23 @@
 # ABOUTME: Handles multi-monitor setup: power menu on primary, wallpaper on secondary monitors.
 
 import logging
+import os
 import sys
 from importlib.resources import files
 
+# gtk4-layer-shell must be loaded before libwayland-client.
+# Only allow our own library in LD_PRELOAD — discard anything inherited from the environment.
+_LAYER_SHELL_LIB = "/usr/lib/libgtk4-layer-shell.so"
+_existing_preload = os.environ.get("LD_PRELOAD", "")
+_is_testing = "pytest" in sys.modules or "unittest" in sys.modules
+if (
+    not _is_testing
+    and _LAYER_SHELL_LIB not in _existing_preload
+    and os.path.exists(_LAYER_SHELL_LIB)
+):
+    os.environ["LD_PRELOAD"] = _LAYER_SHELL_LIB
+    os.execvp(sys.executable, [sys.executable, "-m", "moonset.main"] + sys.argv[1:])
+
 import gi
 gi.require_version("Gtk", "4.0")
 gi.require_version("Gdk", "4.0")