diff --git a/nix/deku-p/deku.nix b/nix/deku-p/deku.nix
index 2f8a02777c..40603f60a9 100644
--- a/nix/deku-p/deku.nix
+++ b/nix/deku-p/deku.nix
@@ -95,6 +95,7 @@ in
           ezgzip
           ppx_jane # TODO: do we need this?
           core
+          core_unix
         ]
         # checkInputs are here because when cross compiling dune needs test dependencies
         # but they are not available for the build phase. The issue can be seen by adding strictDeps = true;.