diff --git a/php/utils/room-icons.php b/php/utils/room-icons.php
index 66479fa..eef02b4 100644
--- a/php/utils/room-icons.php
+++ b/php/utils/room-icons.php
@@ -37,7 +37,6 @@
      * @return string Relative path or null if icon is absent.
      */
     function room_icon(\CommunityRoom $room, string $size): ?string {
-        global $ICON_ALLOWLIST;
         list($width, $height) = explode("x", $size);
         $width = intval($width);
         $height = intval($height);
@@ -48,13 +47,10 @@
         $room_id = $room->get_room_identifier();
         $icon_cached = room_icon_path($room_id);
         $icon_resized = room_icon_path_resized($room_id, $size);
-        if (file_exists($icon_resized)) {
-            if (empty(file_get_contents($icon_resized))) {
-                return "";
-            }
-            return room_icon_path_relative($room_id, $size);
-        }
-        if (!file_exists($icon_cached)) {
+        $icon_expired = file_exists($icon_cached) && filemtime($icon_cached) < strtotime("-1 hour");
+
+        // Re-fetch icons periodically.
+        if (!file_exists($icon_cached) || $icon_expired) {
             $icon_url = $room->get_icon_url();
             if (empty($icon_url)) {
                 return null;
@@ -64,19 +60,26 @@
             if (empty($icon)) {
                 log_info("$room_id returned empty icon.");
             }
-            // Cache result, no matter if empty
-            file_put_contents($icon_cached, $icon);
+            // Never overwrite with an empty file.
+            if (!(file_exists($icon_cached) && empty($icon))) {
+                file_put_contents($icon_cached, $icon);
+            }
         }
-        $icon_cached_contents = file_get_contents($icon_cached);
-        if (empty($icon_cached_contents)) {
-            file_put_contents($icon_resized, "");
-            return "";
+        if (!file_exists($icon_resized) || $icon_expired) {
+            $icon_cached_contents = file_get_contents($icon_cached);
+            if (empty($icon_cached_contents)) {
+                file_put_contents($icon_resized, "");
+                return "";
+            }
+            // Resize image
+            $gd_image = imagecreatefromstring($icon_cached_contents);
+            $gd_resized = imagescale($gd_image, $width, $height);
+            if (!imagewebp($gd_resized, $icon_resized)) {
+                log_info("Converting image for $room_id to $size failed");
+            }
         }
-        // Resize image
-        $gd_image = imagecreatefromstring($icon_cached_contents);
-        $gd_resized = imagescale($gd_image, $width, $height);
-        if (!imagewebp($gd_resized, $icon_resized)) {
-            log_info("Converting image for $room_id to $size failed");
+        if (filesize($icon_resized) == 0) {
+            return "";
         }
         return room_icon_path_relative($room_id, $size);
     }