diff --git a/nixos/lib/utils.nix b/nixos/lib/utils.nix
index 692f0aac40a4..487b20f53d8c 100644
--- a/nixos/lib/utils.nix
+++ b/nixos/lib/utils.nix
@@ -43,6 +43,8 @@ in
 
 let
   hasSlashSuffix = hasSuffix "/";
+  isAbsolute = hasPrefix "/";
+
   # normalisePath adds a slash at the end of the path if it didn't already
   # have one.
   #
@@ -62,6 +64,7 @@ let
       mountPoint = normalisePath mount.mountPoint;
       depends = map normalisePath mount.depends;
     };
+
   utils = rec {
 
     # Copy configuration files to avoid having the entire sources in the system closure
@@ -115,7 +118,6 @@ let
       in
       s:
       let
-        isAbsolute = hasPrefix "/" s;
         # path_simplify(): collapse duplicate slashes and drop "." components.
         rawComponents = filter (c: c != "" && c != ".") (splitString "/" s);
         # systemd accepts ".." only where it is redundant: a leading ".." in an
@@ -128,7 +130,7 @@ let
               acc: c:
               if c == ".." then
                 # A leading ".." in an absolute path is the only redundant case.
-                if isAbsolute && acc.components == [ ] then acc else acc // { normalized = false; }
+                if isAbsolute s && acc.components == [ ] then acc else acc // { normalized = false; }
               else
                 acc // { components = acc.components ++ [ c ]; }
             )
@@ -144,7 +146,7 @@ let
           else if simplified.components != [ ] then
             concatStringsSep "/" simplified.components
           # The root directory, and - matching systemd-escape - the empty string.
-          else if isAbsolute || s == "" then
+          else if isAbsolute s || s == "" then
             "/"
           # A relative path that reduces to nothing (e.g. "."), which has no
           # valid escaping.