Try #1786:

Author: iohk-bors[bot]

test/ghcjs-overlay/default.nix

@@ -6,14 +6,17 @@ let
   project = cabalProject' {
     src = testSrc "ghcjs-overlay";
     inherit compiler-nix-name evalPackages;
-    cabalProjectLocal = lib.optionalString stdenv.hostPlatform.isGhcjs ''
-      repository ghcjs-overlay
-        url: https://raw.githubusercontent.com/input-output-hk/hackage-overlay-ghcjs/bfc363b9f879c360e0a0460ec0c18ec87222ec32
-        secure: True
-        root-keys:
-        key-threshold: 0
-        --sha256: sha256-y1vQnXI1XzkjnC4h66tVDmu2TZjZPcMrZEnE3m0XOfg=
-    '';
+    cabalProjectLocal = if stdenv.hostPlatform.isGhcjs then ''
+        repository ghcjs-overlay
+          url: https://raw.githubusercontent.com/input-output-hk/hackage-overlay-ghcjs/67e08ddf1d405f6a858b5dbb4ef0e9e59c5809db
+          secure: True
+          root-keys:
+          key-threshold: 0
+          --sha256: sha256-y1vQnXI1XzkjnC4h66tVDmu2TZjZPcMrZE003m0XOfg=
+      ''
+      else ''
+        allow-newer: double-conversion:bytestring
+      '';
     # Alternative to the --sha256 comment in cabal.project
     # sha256map = {
     #  "https://raw.githubusercontent.com/input-output-hk/hackage-overlay-ghcjs/bfc363b9f879c360e0a0460ec0c18ec87222ec32" =