diff --git a/pkgs/build-support/replace-vars/default.nix b/pkgs/build-support/replace-vars/default.nix
index a6fc94f4f376d..0053b5e7c6162 100644
--- a/pkgs/build-support/replace-vars/default.nix
+++ b/pkgs/build-support/replace-vars/default.nix
@@ -1,18 +1,24 @@
-{ lib, stdenvNoCC }:
+{
+  lib,
+  stdenvNoCC,
+  doCheck ? true,
+}:
 
 /**
-  `replaceVars` is a wrapper around the [bash function `substitute`](https://nixos.org/manual/nixpkgs/stable/#fun-substitute)
+  `replaceVars` is a wrapper around the [bash function `substitute`](https://nixos.org/manual/nixpkgs/unstable/#fun-substitute)
   in the stdenv. It allows for terse replacement of names in the specified path, while checking
   for common mistakes such as naming a replacement that does nothing or forgetting a variable which
   needs to be replaced.
 
-  As with the [`--subst-var-by`](https://nixos.org/manual/nixpkgs/stable/#fun-substitute-subst-var-by)
+  As with the [`--subst-var-by`](https://nixos.org/manual/nixpkgs/unstable/#fun-substitute-subst-var-by)
   flag, names are encoded as `@name@` in the provided file at the provided path.
 
   Any unmatched variable names in the file at the provided path will cause a build failure.
 
   Any remaining text that matches `@[A-Za-z_][0-9A-Za-z_'-]@` in the output after replacement
-  has occurred will cause a build failure.
+  has occurred will cause a build failure. In the case this step is not desired, use
+  `replaceVars.withoutCheck`, which has the same semantics but doesn't have a check phase making
+  the assertion about remaining unreplaced variables.
 
   # Inputs
 
@@ -20,15 +26,65 @@
   : The file in which to replace variables.
 
   `attrs` (AttrsOf String)
-  : Each entry in this set corresponds to a `--subst-var-by` entry in [`substitute`](https://nixos.org/manual/nixpkgs/stable/#fun-substitute).
+  : Each entry in this set corresponds to a `--subst-var-by` entry in [`substitute`](https://nixos.org/manual/nixpkgs/unstable/#fun-substitute).
 
-  # Example
+  # Examples
+
+  ## `replaceVars`
+
+  Given a file `greeting.txt` that contains the following contents:
+
+  ```
+  @greeting@! Have you heard about the way of the Jedi?
+  ```
+
+  And a derivation that looks like this:
 
   ```nix
   { replaceVars }:
 
-  replaceVars ./greeting.txt { world = "hello"; }
+  replaceVars ./greeting.txt { greeting = "Hello there"; }
+  ```
+
+  The resulting file in `$out` contains this text:
+
+  ```
+  Hello there! Have you heard about the way of the Jedi?
+  ```
+
+  ## `replaceVars.withoutCheck`
+
+  Given a file named `template.json` that contains the following contents:
+
   ```
+  {
+    "key": "@key@",
+    "value": @value@
+  }
+  ```
+
+  And a derivation that looks like this:
+
+  ```nix
+  { replaceVars }:
+
+  replaceVars.withoutCheck ./template.json { key = "master"; }
+  ```
+
+  The resulting file in `$out` contains this text:
+
+  ```
+  {
+    "key": "master",
+    "value": @value@
+  }
+  ```
+
+  This allows chaining together `replaceVars` calls in subsequent derivations or the use of the
+  `substituteInPlace` stdenv function to complete the replacements, at the cost of potentially
+  leaving unreplaced material in the output.
+
+  # Tests
 
   See `../../test/replace-vars/default.nix` for tests of this function.
 */
@@ -48,7 +104,7 @@ in
 stdenvNoCC.mkDerivation {
   name = baseNameOf (toString path);
   src = path;
-  doCheck = true;
+  inherit doCheck;
   dontUnpack = true;
   preferLocalBuild = true;
   allowSubstitutes = false;
diff --git a/pkgs/test/replace-vars/default.nix b/pkgs/test/replace-vars/default.nix
index 76dc81de49c81..b049eefb61730 100644
--- a/pkgs/test/replace-vars/default.nix
+++ b/pkgs/test/replace-vars/default.nix
@@ -27,6 +27,23 @@ in
     '';
   };
 
+  # Success case for `replaceVars.withoutCheck`.
+  replaceVars-without-check = testEqualContents {
+    assertion = "replaceVars-without-check";
+    actual = replaceVars.withoutCheck ./source.txt {
+      "equal in" = "are the same in";
+      brotherhood = "shared humanity";
+    };
+
+    expected = builtins.toFile "expected" ''
+      All human beings are born @free@ and are the same in dignity and rights.
+      They are endowed with reason and conscience and should act towards
+      one another in a spirit of shared humanity.
+
+        -- eroosevelt@humanrights.un.org
+    '';
+  };
+
   # There might eventually be a usecase for this, but it's not supported at the moment.
   replaceVars-fails-on-directory =
     runCommand "replaceVars-fails" { failed = testBuildFailure (replaceVars emptyDirectory { }); }
@@ -43,6 +60,14 @@ in
         touch $out
       '';
 
+  replaceVars-without-check-fails-in-build-phase =
+    runCommand "replaceVars-fails"
+      { failed = testBuildFailure (replaceVars.withoutCheck emptyFile { not-found = "boo~"; }); }
+      ''
+        grep -e "ERROR: pattern @not-found@ doesn't match anything in file.*empty-file" $failed/testBuildFailure.log
+        touch $out
+      '';
+
   replaceVars-fails-in-check-phase =
     runCommand "replaceVars-fails"
       {
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 69e98c04372a4..ea1c1b05c619e 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -1329,7 +1329,9 @@ with pkgs;
 
   replaceDependency = callPackage ../build-support/replace-dependency.nix { };
 
-  replaceVars = callPackage ../build-support/replace-vars { };
+  replaceVars = callPackage ../build-support/replace-vars { } // {
+    withoutCheck = callPackage ../build-support/replace-vars { doCheck = false; };
+  };
 
   nukeReferences = callPackage ../build-support/nuke-references {
     inherit (darwin) signingUtils;