diff --git a/docs/labwc-config.5.scd b/docs/labwc-config.5.scd
index 71b6867b..0307b0e1 100644
--- a/docs/labwc-config.5.scd
+++ b/docs/labwc-config.5.scd
@@ -525,7 +525,10 @@ extending outward from the snapped edge.
 	Should drop-shadows be rendered behind windows. Default is no.
 
 *<theme><dropShadowsOnTiled>* [yes|no]
-	Should drop-shadows be rendered behind tiled windows. Default is no.
+	Should drop-shadows be rendered behind tiled windows. This won't take
+	effect if <core><gap> is smaller than window.active.shadow.size in theme.
+
+	Default is no.
 
 *<theme><font place="">*
 	The font to use for a specific element of a window, menu or OSD.
diff --git a/src/ssd/ssd-shadow.c b/src/ssd/ssd-shadow.c
index 09b8acb9..b77169b7 100644
--- a/src/ssd/ssd-shadow.c
+++ b/src/ssd/ssd-shadow.c
@@ -289,10 +289,19 @@ ssd_shadow_update(struct ssd *ssd)
 	assert(ssd->shadow.tree);
 
 	struct view *view = ssd->view;
+	struct theme *theme = ssd->view->server->theme;
 	bool maximized = view->maximized == VIEW_AXIS_BOTH;
-	bool show_shadows =
-		rc.shadows_enabled && !maximized &&
-		(!view_is_tiled(ssd->view) || rc.shadows_on_tiled);
+	bool tiled_shadows = false;
+	if (rc.shadows_on_tiled) {
+		if (rc.gap >= theme->window[THEME_ACTIVE].shadow_size &&
+			rc.gap >= theme->window[THEME_INACTIVE].shadow_size) {
+			tiled_shadows = true;
+		} else {
+			wlr_log(WLR_INFO, "gap size < shadow_size, ignore rc.shadows_ontiled");
+		}
+	};
+	bool show_shadows = rc.shadows_enabled && !maximized &&
+		(!view_is_tiled(ssd->view) || tiled_shadows);
 	wlr_scene_node_set_enabled(&ssd->shadow.tree->node, show_shadows);
 	if (show_shadows) {
 		set_shadow_geometry(ssd);