diff --git a/src/wayland.rs b/src/wayland.rs
index b00910b..3253d98 100644
--- a/src/wayland.rs
+++ b/src/wayland.rs
@@ -118,7 +118,7 @@ pub fn parse_layer(s: &str) -> Result<Layer> {
         "bottom" => Ok(Layer::Bottom),
         "top" => Ok(Layer::Top),
         "overlay" => Ok(Layer::Overlay),
-        other => bail!("unknown layer: {}", other),
+        other => bail!("unknown layer '{}' (valid: background, bottom, top, overlay)", other),
     }
 }