diff --git a/nixos/modules/services/web-apps/calibre-web.nix b/nixos/modules/services/web-apps/calibre-web.nix
index 82e58873f733..508a1ece72c0 100644
--- a/nixos/modules/services/web-apps/calibre-web.nix
+++ b/nixos/modules/services/web-apps/calibre-web.nix
@@ -160,6 +160,9 @@ in
         after = [ "network.target" ];
         wantedBy = [ "multi-user.target" ];
 
+        # fix book cover cache directory defaults to a path under /nix/store/
+        environment.CACHE_DIR = "/var/cache/calibre-web";
+
         serviceConfig = {
           Type = "simple";
           User = cfg.user;
@@ -181,7 +184,6 @@ in
 
           CacheDirectory = "calibre-web";
           CacheDirectoryMode = "0750";
-          environment.CACHE_DIR = "/var/cache/calibre-web";
         }
         // lib.optionalAttrs (!(lib.hasPrefix "/" cfg.dataDir)) {
           StateDirectory = cfg.dataDir;