diff --git a/nix/package.nix b/nix/package.nix
index af5d192c3..7e31864b7 100644
--- a/nix/package.nix
+++ b/nix/package.nix
@@ -19,9 +19,16 @@ stdenv.mkDerivation rec {
     ++ lib.optional (!bootstrap) [ idris2Bootstrap ];
   buildInputs = [ chez gmp support ];
 
+  # For bootstrap builds the Makefile will try to
+  # rebuild the support library if we don't patch
+  # bootstrap-install.
   prePatch = ''
     patchShebangs --build tests
-    sed 's/$(GIT_SHA1)/${srcRev}/' -i Makefile
+    substituteInPlace Makefile \
+      --replace-fail '$(GIT_SHA1)' '${srcRev}'
+  '' + lib.optionalString bootstrap ''
+    substituteInPlace Makefile \
+      --replace-fail 'bootstrap-install: install-idris2 install-support' 'bootstrap-install: install-idris2'
   '';
 
   makeFlags = [ "IDRIS2_SUPPORT_DIR=${supportLibrariesPath}" ]
diff --git a/nix/support.nix b/nix/support.nix
index 5e20b6ed0..333537332 100644
--- a/nix/support.nix
+++ b/nix/support.nix
@@ -1,5 +1,8 @@
-{ stdenv, lib, gmp, idris2Version }:
-stdenv.mkDerivation rec {
+{ stdenv, lib, overrideSDK, gmp, idris2Version }:
+let
+  stdenv' = if stdenv.isDarwin then overrideSDK stdenv "11.0" else stdenv;
+in
+stdenv'.mkDerivation rec {
   pname = "libidris2_support";
   version = idris2Version;
 
@@ -10,7 +13,7 @@ stdenv.mkDerivation rec {
 
   makeFlags = [
     "PREFIX=$(out)"
-  ] ++ lib.optional stdenv.isDarwin "OS=";
+  ] ++ lib.optional stdenv'.isDarwin "OS=";
 
   buildFlags = [ "support" ];