diff --git a/.git-blame-ignore-revs b/.git-blame-ignore-revs
index 34d3416a238d..7cdd0738a1fd 100644
--- a/.git-blame-ignore-revs
+++ b/.git-blame-ignore-revs
@@ -160,6 +160,9 @@ ad815aebfbfe1415ff6436521d545029c803c3fb
 # nixos/nvidia: apply nixfmt-rfc-style (#313440)
 fbdcdde04a7caa007e825a8b822c75fab9adb2d6
 
+# treewide: reformat files which need reformatting after (#341407)
+e0464e47880a69896f0fb1810f00e0de469f770a
+
 # step-cli: format package.nix with nixfmt (#331629)
 fc7a83f8b62e90de5679e993d4d49ca014ea013d
 
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index b09cbaba14cd..f3c3cfe611d2 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -637,7 +637,7 @@ Names of files and directories should be in lowercase, with dashes between words
 
   ```nix
   {
-    buildInputs = lib.optional stdenv.isDarwin iconv;
+    buildInputs = lib.optional stdenv.hostPlatform.isDarwin iconv;
   }
   ```
 
@@ -645,7 +645,7 @@ Names of files and directories should be in lowercase, with dashes between words
 
   ```nix
   {
-    buildInputs = if stdenv.isDarwin then [ iconv ] else null;
+    buildInputs = if stdenv.hostPlatform.isDarwin then [ iconv ] else null;
   }
   ```
 
diff --git a/doc/languages-frameworks/beam.section.md b/doc/languages-frameworks/beam.section.md
index 3653cdb337d1..2aac65900b9a 100644
--- a/doc/languages-frameworks/beam.section.md
+++ b/doc/languages-frameworks/beam.section.md
@@ -349,8 +349,8 @@ let
     nodePackages.prettier
   ];
 
-  inputs = basePackages ++ lib.optionals stdenv.isLinux [ inotify-tools ]
-    ++ lib.optionals stdenv.isDarwin
+  inputs = basePackages ++ lib.optionals stdenv.hostPlatform.isLinux [ inotify-tools ]
+    ++ lib.optionals stdenv.hostPlatform.isDarwin
     (with darwin.apple_sdk.frameworks; [ CoreFoundation CoreServices ]);
 
   # define shell startup command
diff --git a/doc/languages-frameworks/emscripten.section.md b/doc/languages-frameworks/emscripten.section.md
index 9ce48db2c2de..d1ed62d0503f 100644
--- a/doc/languages-frameworks/emscripten.section.md
+++ b/doc/languages-frameworks/emscripten.section.md
@@ -84,7 +84,7 @@ One advantage is that when `pkgs.zlib` is updated, it will automatically update
     echo "================= /testing zlib using node ================="
   '';
 
-  postPatch = pkgs.lib.optionalString pkgs.stdenv.isDarwin ''
+  postPatch = pkgs.lib.optionalString pkgs.stdenv.hostPlatform.isDarwin ''
     substituteInPlace configure \
       --replace-fail '/usr/bin/libtool' 'ar' \
       --replace-fail 'AR="libtool"' 'AR="ar"' \
diff --git a/doc/languages-frameworks/perl.section.md b/doc/languages-frameworks/perl.section.md
index a3d76a44f656..843d46584cdd 100644
--- a/doc/languages-frameworks/perl.section.md
+++ b/doc/languages-frameworks/perl.section.md
@@ -125,8 +125,8 @@ On Darwin, if a script has too many `-Idir` flags in its first line (its “sheb
       hash = "sha256-vOhB/FwQMC8PPvdnjDvxRpU6jAZcC6GMQfc0AH4uwKg=";
     };
 
-    nativeBuildInputs = lib.optional stdenv.isDarwin shortenPerlShebang;
-    postInstall = lib.optionalString stdenv.isDarwin ''
+    nativeBuildInputs = lib.optional stdenv.hostPlatform.isDarwin shortenPerlShebang;
+    postInstall = lib.optionalString stdenv.hostPlatform.isDarwin ''
       shortenPerlShebang $out/bin/exiftool
     '';
   };
diff --git a/doc/languages-frameworks/python.section.md b/doc/languages-frameworks/python.section.md
index e0127bd3d47d..3d9736da7fa0 100644
--- a/doc/languages-frameworks/python.section.md
+++ b/doc/languages-frameworks/python.section.md
@@ -1306,7 +1306,7 @@ for example:
   ] ++ lib.optionals (pythonAtLeast "3.8") [
     # broken due to python3.8 async changes
     "async"
-  ] ++ lib.optionals stdenv.isDarwin [
+  ] ++ lib.optionals stdenv.buildPlatform.isDarwin [
     # can fail when building with other packages
     "socket"
   ];
diff --git a/doc/stdenv/platform-notes.chapter.md b/doc/stdenv/platform-notes.chapter.md
index 409c9f2e7b2e..9b0fdd149f9a 100644
--- a/doc/stdenv/platform-notes.chapter.md
+++ b/doc/stdenv/platform-notes.chapter.md
@@ -22,7 +22,7 @@ Some common issues when packaging software for Darwin:
   stdenv.mkDerivation {
     name = "libfoo-1.2.3";
     # ...
-    makeFlags = lib.optional stdenv.isDarwin "LDFLAGS=-Wl,-install_name,$(out)/lib/libfoo.dylib";
+    makeFlags = lib.optional stdenv.hostPlatform.isDarwin "LDFLAGS=-Wl,-install_name,$(out)/lib/libfoo.dylib";
   }
   ```