diff --git a/pkgs/stdenv/darwin/default.nix b/pkgs/stdenv/darwin/default.nix
index a6f927c287da..6fbd78c422da 100644
--- a/pkgs/stdenv/darwin/default.nix
+++ b/pkgs/stdenv/darwin/default.nix
@@ -75,7 +75,7 @@ rec {
     inherit (bootstrapFiles) mkdir bzip2 cpio tarball;
 
     __impureHostDeps = commonImpureHostDeps;
-  } // lib.optionalAttrs (config.contentAddressedByDefault or false) {
+  } // lib.optionalAttrs config.contentAddressedByDefault {
     __contentAddressed = true;
     outputHashAlgo = "sha256";
     outputHashMode = "recursive";
diff --git a/pkgs/stdenv/freebsd/default.nix b/pkgs/stdenv/freebsd/default.nix
index ddcdc6a66e08..de6608587605 100644
--- a/pkgs/stdenv/freebsd/default.nix
+++ b/pkgs/stdenv/freebsd/default.nix
@@ -182,7 +182,7 @@ in
       buildInputs = [ make ];
       mkdir = "/bin/mkdir";
       ln = "/bin/ln";
-    } // lib.optionalAttrs (config.contentAddressedByDefault or false) {
+    } // lib.optionalAttrs config.contentAddressedByDefault {
       __contentAddressed = true;
       outputHashAlgo = "sha256";
       outputHashMode = "recursive";
diff --git a/pkgs/stdenv/generic/default.nix b/pkgs/stdenv/generic/default.nix
index 4fb98e5e8013..5f49aca5aa91 100644
--- a/pkgs/stdenv/generic/default.nix
+++ b/pkgs/stdenv/generic/default.nix
@@ -90,7 +90,7 @@ let
       allowedRequisites = allowedRequisites
         ++ defaultNativeBuildInputs ++ defaultBuildInputs;
     }
-    // lib.optionalAttrs (config.contentAddressedByDefault or false) {
+    // lib.optionalAttrs config.contentAddressedByDefault {
       __contentAddressed = true;
       outputHashAlgo = "sha256";
       outputHashMode = "recursive";
diff --git a/pkgs/stdenv/generic/make-derivation.nix b/pkgs/stdenv/generic/make-derivation.nix
index edfb43f7cd07..d1b93874a25a 100644
--- a/pkgs/stdenv/generic/make-derivation.nix
+++ b/pkgs/stdenv/generic/make-derivation.nix
@@ -93,7 +93,7 @@ in
 
 , __contentAddressed ?
   (! attrs ? outputHash) # Fixed-output drvs can't be content addressed too
-  && (config.contentAddressedByDefault or false)
+  && config.contentAddressedByDefault
 
 , ... } @ attrs:
 
diff --git a/pkgs/stdenv/linux/default.nix b/pkgs/stdenv/linux/default.nix
index e9104dd88cfa..5c5ca64b1e95 100644
--- a/pkgs/stdenv/linux/default.nix
+++ b/pkgs/stdenv/linux/default.nix
@@ -66,7 +66,7 @@ let
   bootstrapTools = import (if localSystem.libc == "musl" then ./bootstrap-tools-musl else ./bootstrap-tools) {
     inherit system bootstrapFiles;
     extraAttrs = lib.optionalAttrs
-      (config.contentAddressedByDefault or false)
+      config.contentAddressedByDefault
       {
         __contentAddressed = true;
         outputHashAlgo = "sha256";
diff --git a/pkgs/stdenv/linux/make-bootstrap-tools.nix b/pkgs/stdenv/linux/make-bootstrap-tools.nix
index 2263341b23fc..d23a996dfcb4 100644
--- a/pkgs/stdenv/linux/make-bootstrap-tools.nix
+++ b/pkgs/stdenv/linux/make-bootstrap-tools.nix
@@ -235,7 +235,7 @@ in with pkgs; rec {
 
   bootstrapTools =
     let extraAttrs = lib.optionalAttrs
-      (config.contentAddressedByDefault or false)
+      config.contentAddressedByDefault
       {
         __contentAddressed = true;
         outputHashAlgo = "sha256";
diff --git a/pkgs/top-level/config.nix b/pkgs/top-level/config.nix
index 98e87d7f5ace..1ee44a47af9f 100644
--- a/pkgs/top-level/config.nix
+++ b/pkgs/top-level/config.nix
@@ -36,6 +36,10 @@ let
       feature = "set <literal>strictDeps</literal> to true by default";
     };
 
+    contentAddressedByDefault = mkMassRebuild {
+      feature = "set <literal>__contentAddressed</literal> to true by default";
+    };
+
     allowAliases = mkOption {
       type = types.bool;
       default = true;