diff --git a/nixos/modules/system/etc/etc.nix b/nixos/modules/system/etc/etc.nix
index baf37ba6def3..9f735364196c 100644
--- a/nixos/modules/system/etc/etc.nix
+++ b/nixos/modules/system/etc/etc.nix
@@ -238,7 +238,9 @@ in
       # this should not run because /etc is mounted via a systemd mount unit
       # instead. To a large extent this mimics what composefs does. Because
       # it's relatively simple, however, we avoid the composefs dependency.
-      if [[ ! $IN_NIXOS_SYSTEMD_STAGE1 ]]; then
+      # Since this script is not idempotent, it should not run when etc hasn't
+      # changed.
+      if [[ ! $IN_NIXOS_SYSTEMD_STAGE1 ]] && [[ "${config.system.build.etc}/etc" != "$(readlink -f /run/current-system/etc)" ]]; then
         echo "remounting /etc..."
 
         tmpMetadataMount=$(mktemp --directory)
diff --git a/nixos/tests/activation/etc-overlay-immutable.nix b/nixos/tests/activation/etc-overlay-immutable.nix
index 70c3623b929c..f347f9cf8efe 100644
--- a/nixos/tests/activation/etc-overlay-immutable.nix
+++ b/nixos/tests/activation/etc-overlay-immutable.nix
@@ -20,11 +20,17 @@
   };
 
   testScript = ''
-    machine.succeed("findmnt --kernel --type overlay /etc")
-    machine.fail("stat /etc/newgen")
+    with subtest("/etc is mounted as an overlay"):
+      machine.succeed("findmnt --kernel --type overlay /etc")
 
-    machine.succeed("/run/current-system/specialisation/new-generation/bin/switch-to-configuration switch")
+    with subtest("switching to the same generation"):
+      machine.succeed("/run/current-system/bin/switch-to-configuration test")
 
-    assert machine.succeed("cat /etc/newgen") == "newgen"
+    with subtest("switching to a new generation"):
+      machine.fail("stat /etc/newgen")
+
+      machine.succeed("/run/current-system/specialisation/new-generation/bin/switch-to-configuration switch")
+
+      assert machine.succeed("cat /etc/newgen") == "newgen"
   '';
 }
diff --git a/nixos/tests/activation/etc-overlay-mutable.nix b/nixos/tests/activation/etc-overlay-mutable.nix
index cfe7604fceb8..087c06408a71 100644
--- a/nixos/tests/activation/etc-overlay-mutable.nix
+++ b/nixos/tests/activation/etc-overlay-mutable.nix
@@ -18,13 +18,19 @@
   };
 
   testScript = ''
-    machine.succeed("findmnt --kernel --type overlay /etc")
-    machine.fail("stat /etc/newgen")
-    machine.succeed("echo -n 'mutable' > /etc/mutable")
+    with subtest("/etc is mounted as an overlay"):
+      machine.succeed("findmnt --kernel --type overlay /etc")
 
-    machine.succeed("/run/current-system/specialisation/new-generation/bin/switch-to-configuration switch")
+    with subtest("switching to the same generation"):
+      machine.succeed("/run/current-system/bin/switch-to-configuration test")
 
-    assert machine.succeed("cat /etc/newgen") == "newgen"
-    assert machine.succeed("cat /etc/mutable") == "mutable"
+    with subtest("switching to a new generation"):
+      machine.fail("stat /etc/newgen")
+      machine.succeed("echo -n 'mutable' > /etc/mutable")
+
+      machine.succeed("/run/current-system/specialisation/new-generation/bin/switch-to-configuration switch")
+
+      assert machine.succeed("cat /etc/newgen") == "newgen"
+      assert machine.succeed("cat /etc/mutable") == "mutable"
   '';
 }