diff --git a/src/picom.c b/src/picom.c
index a7bc763..b4a4d49 100644
--- a/src/picom.c
+++ b/src/picom.c
@@ -374,34 +374,6 @@ static void recheck_focus(session_t *ps) {
 	}
 }
 
-/**
- * Look for the client window of a particular window.
- */
-xcb_window_t find_client_win(session_t *ps, xcb_window_t w) {
-	if (wid_has_prop(ps, w, ps->atoms->aWM_STATE)) {
-		return w;
-	}
-
-	xcb_query_tree_reply_t *reply =
-	    xcb_query_tree_reply(ps->c, xcb_query_tree(ps->c, w), NULL);
-	if (!reply)
-		return 0;
-
-	xcb_window_t *children = xcb_query_tree_children(reply);
-	int nchildren = xcb_query_tree_children_length(reply);
-	int i;
-	xcb_window_t ret = 0;
-
-	for (i = 0; i < nchildren; ++i) {
-		if ((ret = find_client_win(ps, children[i])))
-			break;
-	}
-
-	free(reply);
-
-	return ret;
-}
-
 /**
  * Rebuild cached <code>screen_reg</code>.
  */
diff --git a/src/picom.h b/src/picom.h
index fb64fda..fe39ded 100644
--- a/src/picom.h
+++ b/src/picom.h
@@ -42,8 +42,6 @@ void add_damage(session_t *ps, const region_t *damage);
 
 uint32_t determine_evmask(session_t *ps, xcb_window_t wid, win_evmode_t mode);
 
-xcb_window_t find_client_win(session_t *ps, xcb_window_t w);
-
 void circulate_win(session_t *ps, xcb_circulate_notify_event_t *ce);
 
 void update_refresh_rate(session_t *ps);
diff --git a/src/win.c b/src/win.c
index 2da27eb..a27643c 100644
--- a/src/win.c
+++ b/src/win.c
@@ -1046,6 +1046,34 @@ void win_unmark_client(session_t *ps, struct managed_win *w) {
 	    (const uint32_t[]){determine_evmask(ps, client, WIN_EVMODE_UNKNOWN)});
 }
 
+/**
+ * Look for the client window of a particular window.
+ */
+static xcb_window_t find_client_win(session_t *ps, xcb_window_t w) {
+	if (wid_has_prop(ps, w, ps->atoms->aWM_STATE)) {
+		return w;
+	}
+
+	xcb_query_tree_reply_t *reply =
+	    xcb_query_tree_reply(ps->c, xcb_query_tree(ps->c, w), NULL);
+	if (!reply)
+		return 0;
+
+	xcb_window_t *children = xcb_query_tree_children(reply);
+	int nchildren = xcb_query_tree_children_length(reply);
+	int i;
+	xcb_window_t ret = 0;
+
+	for (i = 0; i < nchildren; ++i) {
+		if ((ret = find_client_win(ps, children[i])))
+			break;
+	}
+
+	free(reply);
+
+	return ret;
+}
+
 /**
  * Recheck client window of a window.
  *