diff --git a/pkgs/build-support/rust/build-rust-crate/build-crate.nix b/pkgs/build-support/rust/build-rust-crate/build-crate.nix
index 0978f7e1756f..2999c3d4c1d9 100644
--- a/pkgs/build-support/rust/build-rust-crate/build-crate.nix
+++ b/pkgs/build-support/rust/build-rust-crate/build-crate.nix
@@ -11,7 +11,7 @@
     rustcOpts =
       lib.lists.foldl' (opts: opt: opts + " " + opt)
         (if release then "-C opt-level=3" else "-C debuginfo=2")
-        (["-C codegen-units=1"] ++ extraRustcOpts);
+        (["-C codegen-units=$NIX_BUILD_CORES"] ++ extraRustcOpts);
     rustcMeta = "-C metadata=${metadata} -C extra-filename=-${metadata}";
 
     # Some platforms have different names for rustc.
diff --git a/pkgs/build-support/rust/build-rust-crate/configure-crate.nix b/pkgs/build-support/rust/build-rust-crate/configure-crate.nix
index b184d363d554..165b3414c6a3 100644
--- a/pkgs/build-support/rust/build-rust-crate/configure-crate.nix
+++ b/pkgs/build-support/rust/build-rust-crate/configure-crate.nix
@@ -22,7 +22,7 @@ let version_ = lib.splitString "-" crateVersion;
     version = lib.splitString "." (lib.head version_);
     rustcOpts = lib.lists.foldl' (opts: opt: opts + " " + opt)
         (if release then "-C opt-level=3" else "-C debuginfo=2")
-        (["-C codegen-units=1"] ++ extraRustcOpts);
+        (["-C codegen-units=$NIX_BUILD_CORES"] ++ extraRustcOpts);
     buildDeps = makeDeps buildDependencies;
     authors = lib.concatStringsSep ":" crateAuthors;
     optLevel = if release then 3 else 0;