diff --git a/pkgs/by-name/ei/eigen_5/package.nix b/pkgs/by-name/ei/eigen_5/package.nix
index 9e03b7c319d4..83c2928b6eb6 100644
--- a/pkgs/by-name/ei/eigen_5/package.nix
+++ b/pkgs/by-name/ei/eigen_5/package.nix
@@ -52,6 +52,9 @@ stdenv.mkDerivation (finalAttrs: {
   ];
 
   postInstall = lib.optionalString withDoc ''
+    # Fontconfig error: No writable cache directories
+    export XDG_CACHE_HOME="$(mktemp -d)"
+
     cmake --build . -t install-doc
   '';