diff --git a/src/event.c b/src/event.c
index 77b20cadaf..67cdaaaffa 100644
--- a/src/event.c
+++ b/src/event.c
@@ -277,9 +277,6 @@ static void configure_win(session_t *ps, xcb_configure_notify_event_t *ce) {
 			w->pending_g.border_width = ce->border_width;
 			win_set_flags(w, WIN_FLAGS_SIZE_STALE);
 		}
-
-		// Recalculate which monitor this window is on
-		win_update_monitor(&ps->monitors, w);
 	}
 
 	// override_redirect flag cannot be changed after window creation, as far
diff --git a/src/render.c b/src/render.c
index 1e80623ae6..a20651954a 100644
--- a/src/render.c
+++ b/src/render.c
@@ -1121,18 +1121,20 @@ void paint_all(session_t *ps, struct win *t) {
 				pixman_region32_subtract(&reg_tmp, &reg_tmp, &bshape_no_corners);
 			}
 
-			if (ps->o.crop_shadow_to_monitor && w->randr_monitor >= 0 &&
-			    w->randr_monitor < ps->monitors.count) {
-				// There can be a window where number of monitors is
-				// updated, but the monitor number attached to the window
-				// have not.
-				//
-				// Window monitor number will be updated eventually, so
-				// here we just check to make sure we don't access out of
-				// bounds.
-				pixman_region32_intersect(
-				    &reg_tmp, &reg_tmp,
-				    &ps->monitors.regions[w->randr_monitor]);
+			if (ps->o.crop_shadow_to_monitor) {
+				auto monitor_index = win_find_monitor(&ps->monitors, w);
+				if (monitor_index >= 0) {
+					// There can be a window where number of monitors
+					// is updated, but the monitor number attached to
+					// the window have not.
+					//
+					// Window monitor number will be updated
+					// eventually, so here we just check to make sure
+					// we don't access out of bounds.
+					pixman_region32_intersect(
+					    &reg_tmp, &reg_tmp,
+					    &ps->monitors.regions[monitor_index]);
+				}
 			}
 
 			// Detect if the region is empty before painting
diff --git a/src/renderer/command_builder.c b/src/renderer/command_builder.c
index b4228cd435..a2aa1b9614 100644
--- a/src/renderer/command_builder.c
+++ b/src/renderer/command_builder.c
@@ -135,9 +135,12 @@ command_for_shadow(struct layer *layer, struct backend_command *cmd,
 		}
 	}
 	log_region(TRACE, &cmd->target_mask);
-	if (monitors && w->randr_monitor >= 0 && w->randr_monitor < monitors->count) {
-		pixman_region32_intersect(&cmd->target_mask, &cmd->target_mask,
-		                          &monitors->regions[w->randr_monitor]);
+	if (monitors) {
+		auto monitor_index = win_find_monitor(monitors, w);
+		if (monitor_index >= 0) {
+			pixman_region32_intersect(&cmd->target_mask, &cmd->target_mask,
+			                          &monitors->regions[monitor_index]);
+		}
 	}
 	log_region(TRACE, &cmd->target_mask);
 	if (w->corner_radius > 0) {
diff --git a/src/wm/win.c b/src/wm/win.c
index af3bde3055..eef92171dc 100644
--- a/src/wm/win.c
+++ b/src/wm/win.c
@@ -538,8 +538,6 @@ void win_process_update_flags(session_t *ps, struct win *w) {
 			damaged = true;
 			win_clear_flags(w, WIN_FLAGS_POSITION_STALE);
 		}
-
-		win_update_monitor(&ps->monitors, w);
 	}
 
 	if (win_check_flags_all(w, WIN_FLAGS_PROPERTY_STALE)) {
@@ -1401,7 +1399,6 @@ struct win *win_maybe_allocate(session_t *ps, struct wm_ref *cursor) {
 	    .focused_force = UNSET,
 	    .invert_color_force = UNSET,
 
-	    .randr_monitor = -1,
 	    .mode = WMODE_TRANS,
 	    .leader = XCB_NONE,
 	    .cache_leader = XCB_NONE,
@@ -1983,9 +1980,10 @@ void unmap_win_start(struct win *w) {
 }
 
 struct win_script_context win_script_context_prepare(struct session *ps, struct win *w) {
+	auto monitor_index = win_find_monitor(&ps->monitors, w);
 	auto monitor =
-	    (w->randr_monitor >= 0 && w->randr_monitor < ps->monitors.count)
-	        ? *pixman_region32_extents(&ps->monitors.regions[w->randr_monitor])
+	    monitor_index >= 0
+	        ? *pixman_region32_extents(&ps->monitors.regions[monitor_index])
 	        : (pixman_box32_t){
 	              .x1 = 0, .y1 = 0, .x2 = ps->root_width, .y2 = ps->root_height};
 	struct win_script_context ret = {
@@ -2158,24 +2156,23 @@ bool win_process_animation_and_state_change(struct session *ps, struct win *w, d
 
 #undef WSTATE_PAIR
 
-// TODO(absolutelynothelix): rename to x_update_win_(randr_?)monitor and move to
-// the x.c.
-void win_update_monitor(struct x_monitors *monitors, struct win *mw) {
-	mw->randr_monitor = -1;
+/// Find which monitor a window is on.
+int win_find_monitor(const struct x_monitors *monitors, const struct win *mw) {
+	int ret = -1;
 	for (int i = 0; i < monitors->count; i++) {
 		auto e = pixman_region32_extents(&monitors->regions[i]);
 		if (e->x1 <= mw->g.x && e->y1 <= mw->g.y &&
 		    e->x2 >= mw->g.x + mw->widthb && e->y2 >= mw->g.y + mw->heightb) {
-			mw->randr_monitor = i;
 			log_debug("Window %#010x (%s), %dx%d+%dx%d, is entirely on the "
 			          "monitor %d (%dx%d+%dx%d)",
 			          win_id(mw), mw->name, mw->g.x, mw->g.y, mw->widthb,
 			          mw->heightb, i, e->x1, e->y1, e->x2 - e->x1, e->y2 - e->y1);
-			return;
+			return i;
 		}
 	}
 	log_debug("Window %#010x (%s), %dx%d+%dx%d, is not entirely on any monitor",
 	          win_id(mw), mw->name, mw->g.x, mw->g.y, mw->widthb, mw->heightb);
+	return ret;
 }
 
 /// Start the mapping of a window. We cannot map immediately since we might need to fade
diff --git a/src/wm/win.h b/src/wm/win.h
index d82a0fb90b..9e498e3591 100644
--- a/src/wm/win.h
+++ b/src/wm/win.h
@@ -114,8 +114,6 @@ struct win {
 	struct win_geometry g;
 	/// Updated geometry received in events
 	struct win_geometry pending_g;
-	/// X RandR monitor this window is on.
-	int randr_monitor;
 	/// Window visual pict format
 	const xcb_render_pictforminfo_t *pictfmt;
 	/// Client window visual pict format
@@ -372,7 +370,7 @@ void win_on_client_update(session_t *ps, struct win *w);
 
 bool attr_pure win_should_dim(session_t *ps, const struct win *w);
 
-void win_update_monitor(struct x_monitors *monitors, struct win *mw);
+int attr_pure win_find_monitor(const struct x_monitors *monitors, const struct win *mw);
 
 /// Recheck if a window is fullscreen
 void win_update_is_fullscreen(const session_t *ps, struct win *w);