diff --git a/pkgs/applications/networking/instant-messengers/riot/riot-web.nix b/pkgs/applications/networking/instant-messengers/riot/riot-web.nix
index 61a581e834c1..2d6c0df412a1 100644
--- a/pkgs/applications/networking/instant-messengers/riot/riot-web.nix
+++ b/pkgs/applications/networking/instant-messengers/riot/riot-web.nix
@@ -3,7 +3,6 @@
 # Note for maintainers:
 # Versions of `riot-web` and `riot-desktop` should be kept in sync.
 
-let configFile = writeText "riot-config.json" conf; in
 stdenv.mkDerivation rec {
   name= "riot-web-${version}";
   version = "1.2.2";
@@ -13,10 +12,14 @@ stdenv.mkDerivation rec {
     sha256 = "19nb6gyjaijah068ika6hvk18hraivm71830i9cd4ssl6g5j4k8x";
   };
 
-  installPhase = ''
+  installPhase = let
+    configFile = if (conf != null)
+      then writeText "riot-config.json" conf
+      else "$out/config.sample.json";
+  in ''
     mkdir -p $out/
     cp -R . $out/
-    ${lib.optionalString (conf != null) "ln -s ${configFile} $out/config.json"}
+    ln -s ${configFile} $out/config.json
   '';
 
   meta = {