diff --git a/nixos/lib/systemd-lib.nix b/nixos/lib/systemd-lib.nix
index 832160111da4..b67495609ff5 100644
--- a/nixos/lib/systemd-lib.nix
+++ b/nixos/lib/systemd-lib.nix
@@ -525,4 +525,9 @@ in rec {
       )}
     '';
 
+  # The maximum number of characters allowed in a GPT partition label. This
+  # limit is specified by UEFI and enforced by systemd-repart.
+  # Corresponds to GPT_LABEL_MAX from systemd's gpt.h.
+  GPTMaxLabelLength = 36;
+
 }
diff --git a/nixos/modules/system/boot/systemd/repart.nix b/nixos/modules/system/boot/systemd/repart.nix
index 6cc387cb6f43..7771f5fe0678 100644
--- a/nixos/modules/system/boot/systemd/repart.nix
+++ b/nixos/modules/system/boot/systemd/repart.nix
@@ -13,14 +13,14 @@ let
 
   partitionAssertions = lib.mapAttrsToList (fileName: definition:
     let
-      maxLabelLength = 36; # GPT_LABEL_MAX defined in systemd's gpt.h
+      inherit (utils.systemdUtils.lib) GPTMaxLabelLength;
       labelLength = builtins.stringLength definition.Label;
     in
     {
-      assertion = definition ? Label -> maxLabelLength >= labelLength;
+      assertion = definition ? Label -> GPTMaxLabelLength >= labelLength;
       message = ''
         The partition label '${definition.Label}' defined for '${fileName}' is ${toString labelLength}
-        characters long, but the maximum label length supported by systemd is ${toString maxLabelLength}.
+        characters long, but the maximum label length supported by systemd is ${toString GPTMaxLabelLength}.
       '';
     }
   ) cfg.partitions;