diff --git a/pkgs/development/compilers/rust/rustfmt.nix b/pkgs/development/compilers/rust/rustfmt.nix
index 62a6ccbbef1..e564cabd85e 100644
--- a/pkgs/development/compilers/rust/rustfmt.nix
+++ b/pkgs/development/compilers/rust/rustfmt.nix
@@ -7,7 +7,7 @@ rustPlatform.buildRustPackage rec {
   # the rust source tarball already has all the dependencies vendored, no need to fetch them again
   cargoVendorDir = "vendor";
   preBuild = "pushd src/tools/rustfmt";
-  postBuild = "popd";
+  preInstall = "popd";
 
   buildInputs = stdenv.lib.optional stdenv.isDarwin Security;