diff --git a/pkgs/build-support/writers/default.nix b/pkgs/build-support/writers/default.nix
index 2c26f350fbd7..3016a45b8a0f 100644
--- a/pkgs/build-support/writers/default.nix
+++ b/pkgs/build-support/writers/default.nix
@@ -264,8 +264,8 @@ let
   makeScriptWriter {
     interpreter =
       if libraries == []
-      then "${python}/bin/python"
-      else "${python.withPackages (ps: libraries)}/bin/python"
+      then python.interpreter
+      else (python.withPackages (ps: libraries)).interpreter
     ;
     check = optionalString python.isPy3k (writeDash "pythoncheck.sh" ''
       exec ${buildPythonPackages.flake8}/bin/flake8 --show-source ${ignoreAttribute} "$1"
diff --git a/pkgs/test/stdenv/hooks.nix b/pkgs/test/stdenv/hooks.nix
index ba5da511c6fe..eb1b3f61bda6 100644
--- a/pkgs/test/stdenv/hooks.nix
+++ b/pkgs/test/stdenv/hooks.nix
@@ -115,7 +115,7 @@
     name = "test-reproducible-builds";
     buildCommand = ''
       # can't be tested more precisely because the value of random-seed changes depending on the output
-      [[ $env.NIX_CFLAGS_COMPILE =~ "-frandom-seed=" ]]
+      [[ $NIX_CFLAGS_COMPILE =~ "-frandom-seed=" ]]
       touch $out
     '';
   };