diff --git a/nixos/doc/manual/manpages/nixos-build-vms.8 b/nixos/doc/manual/manpages/nixos-build-vms.8
index abf06b5dd596..6a8f2c42eddf 100644
--- a/nixos/doc/manual/manpages/nixos-build-vms.8
+++ b/nixos/doc/manual/manpages/nixos-build-vms.8
@@ -1,10 +1,6 @@
 .Dd January 1, 1980
-.\" nixpkgs groff will use Nixpkgs as the OS in the title by default, taking it from
-.\" doc-default-operating-system. mandoc doesn't have this register set by default,
-.\" so we can use it as a groff/mandoc switch.
-.ie ddoc-default-operating-system .Dt nixos-build-vms \&8 "NixOS System Manager's Manual"
-.el .Dt nixos-build-vms 8
-.Os NixOS
+.Dt nixos-build-vms 8
+.Os
 .Sh NAME
 .Nm nixos-build-vms
 .Nd build a network of virtual machines from a network of NixOS configurations
diff --git a/nixos/doc/manual/manpages/nixos-enter.8 b/nixos/doc/manual/manpages/nixos-enter.8
index bc8df31e5f2d..646f92199d62 100644
--- a/nixos/doc/manual/manpages/nixos-enter.8
+++ b/nixos/doc/manual/manpages/nixos-enter.8
@@ -1,10 +1,6 @@
 .Dd January 1, 1980
-.\" nixpkgs groff will use Nixpkgs as the OS in the title by default, taking it from
-.\" doc-default-operating-system. mandoc doesn't have this register set by default,
-.\" so we can use it as a groff/mandoc switch.
-.ie ddoc-default-operating-system .Dt nixos-enter \&8 "NixOS System Manager's Manual"
-.el .Dt nixos-enter 8
-.Os NixOS
+.Dt nixos-enter 8
+.Os
 .Sh NAME
 .Nm nixos-enter
 .Nd run a command in a NixOS chroot environment
diff --git a/nixos/doc/manual/manpages/nixos-generate-config.8 b/nixos/doc/manual/manpages/nixos-generate-config.8
index 8b9bb4d42483..1b95599e156a 100644
--- a/nixos/doc/manual/manpages/nixos-generate-config.8
+++ b/nixos/doc/manual/manpages/nixos-generate-config.8
@@ -1,10 +1,6 @@
 .Dd January 1, 1980
-.\" nixpkgs groff will use Nixpkgs as the OS in the title by default, taking it from
-.\" doc-default-operating-system. mandoc doesn't have this register set by default,
-.\" so we can use it as a groff/mandoc switch.
-.ie ddoc-default-operating-system .Dt nixos-generate-config \&8 "NixOS System Manager's Manual"
-.el .Dt nixos-generate-config 8
-.Os NixOS
+.Dt nixos-generate-config 8
+.Os
 .Sh NAME
 .Nm nixos-generate-config
 .Nd generate NixOS configuration modules
diff --git a/nixos/doc/manual/manpages/nixos-install.8 b/nixos/doc/manual/manpages/nixos-install.8
index dc0a5da275d8..c6c8ed15224d 100644
--- a/nixos/doc/manual/manpages/nixos-install.8
+++ b/nixos/doc/manual/manpages/nixos-install.8
@@ -1,10 +1,6 @@
 .Dd January 1, 1980
-.\" nixpkgs groff will use Nixpkgs as the OS in the title by default, taking it from
-.\" doc-default-operating-system. mandoc doesn't have this register set by default,
-.\" so we can use it as a groff/mandoc switch.
-.ie ddoc-default-operating-system .Dt nixos-install \&8 "NixOS System Manager's Manual"
-.el .Dt nixos-install 8
-.Os NixOS
+.Dt nixos-install 8
+.Os
 .Sh NAME
 .Nm nixos-install
 .Nd install bootloader and NixOS
diff --git a/nixos/doc/manual/manpages/nixos-option.8 b/nixos/doc/manual/manpages/nixos-option.8
index 79cc113cfaf2..28438b03580b 100644
--- a/nixos/doc/manual/manpages/nixos-option.8
+++ b/nixos/doc/manual/manpages/nixos-option.8
@@ -1,10 +1,6 @@
 .Dd January 1, 1980
-.\" nixpkgs groff will use Nixpkgs as the OS in the title by default, taking it from
-.\" doc-default-operating-system. mandoc doesn't have this register set by default,
-.\" so we can use it as a groff/mandoc switch.
-.ie ddoc-default-operating-system .Dt nixos-option \&8 "NixOS System Manager's Manual"
-.el .Dt nixos-option 8
-.Os NixOS
+.Dt nixos-option 8
+.Os
 .Sh NAME
 .Nm nixos-option
 .Nd inspect a NixOS configuration
diff --git a/nixos/doc/manual/manpages/nixos-rebuild.8 b/nixos/doc/manual/manpages/nixos-rebuild.8
index 8ff59d6da9cf..64bbbee411d7 100644
--- a/nixos/doc/manual/manpages/nixos-rebuild.8
+++ b/nixos/doc/manual/manpages/nixos-rebuild.8
@@ -1,10 +1,6 @@
 .Dd January 1, 1980
-.\" nixpkgs groff will use Nixpkgs the OS in the title by default, taking it from
-.\" doc-default-operating-system. mandoc doesn't have this register set by default,
-.\" so we can use it as a groff/mandoc switch.
-.ie ddoc-default-operating-system .Dt nixos-rebuild \&8 "NixOS System Manager's Manual"
-.el .Dt nixos-rebuild 8
-.Os NixOS
+.Dt nixos-rebuild 8
+.Os
 .Sh NAME
 .Nm nixos-rebuild
 .Nd reconfigure a NixOS machine
diff --git a/nixos/doc/manual/manpages/nixos-version.8 b/nixos/doc/manual/manpages/nixos-version.8
index 980ee8b1f49e..f661611599fb 100644
--- a/nixos/doc/manual/manpages/nixos-version.8
+++ b/nixos/doc/manual/manpages/nixos-version.8
@@ -1,10 +1,6 @@
 .Dd January 1, 1980
-.\" nixpkgs groff will use Nixpkgs as the OS in the title by default, taking it from
-.\" doc-default-operating-system. mandoc doesn't have this register set by default,
-.\" so we can use it as a groff/mandoc switch.
-.ie ddoc-default-operating-system .Dt nixos-version \&8 "NixOS System Manager's Manual"
-.el .Dt nixos-version 8
-.Os NixOS
+.Dt nixos-version 8
+.Os
 .Sh NAME
 .Nm nixos-version
 .Nd show the NixOS version