diff --git a/check-utils.nix b/check-utils.nix
index 809d3ed..cd2cb76 100644
--- a/check-utils.nix
+++ b/check-utils.nix
@@ -1,7 +1,33 @@
 systemOrPkgs:
 let
-  str = it: if it == null then "null" else (toString it);
+  inherit (builtins) foldl' unsafeDiscardStringContext elemAt match split concatStringsSep isList substring stringLength length attrNames;
   system = systemOrPkgs.system or systemOrPkgs;
+  pipe = val: functions: foldl' (x: f: f x) val functions;
+  max = x: y: if x > y then x else y;
+
+  # Minimized copy-paste https://github.com/NixOS/nixpkgs/blob/master/lib/strings.nix#L746-L762
+  sanitizeDerivationName = string: pipe (toString string) [
+    # Get rid of string context. This is safe under the assumption that the
+    # resulting string is only used as a derivation name
+    unsafeDiscardStringContext
+    # Strip all leading "."
+    (x: elemAt (match "\\.*(.*)" x) 0)
+    # Split out all invalid characters
+    # https://github.com/NixOS/nix/blob/2.3.2/src/libstore/store-api.cc#L85-L112
+    # https://github.com/NixOS/nix/blob/2242be83c61788b9c0736a92bb0b5c7bbfc40803/nix-rust/src/store/path.rs#L100-L125
+    (split "[^[:alnum:]+._?=-]+")
+    # Replace invalid character ranges with a "-"
+    (map (s: if isList s then "-" else s))
+    (concatStringsSep "")
+    # Limit to 211 characters (minus 4 chars for ".drv")
+    (x: substring (max (stringLength x - 207) 0) (-1) x)
+    # If the result is empty, replace it with "?EMPTY?"
+    (x: if stringLength x == 0 then "?EMPTY?" else x)
+  ];
+
+  # Minimized version of 'sanitizeDerivationName' function
+  str = it: if it == null then "null" else (sanitizeDerivationName it);
+
   test = name: command: derivation {
     inherit name system;
     builder = "/bin/sh";
@@ -18,5 +44,5 @@ in
   hasKey = attrset: key:
     if attrset ? ${str key}
     then test "SUCCESS__${str key}__EXISTS_IN_ATTRSET" "echo success > $out"
-    else test "FAILURE__${str key}__DOES_NOT_EXISTS_IN_ATTRSET_SIZE_${str(builtins.length (builtins.attrNames attrset))}" "exit 1";
+    else test "FAILURE__${str key}__DOES_NOT_EXISTS_IN_ATTRSET_SIZE_${str(length (attrNames attrset))}" "exit 1";
 }
diff --git a/examples/checks-utils/flake.nix b/examples/checks-utils/flake.nix
index 4b16e1c..dbaa4f6 100644
--- a/examples/checks-utils/flake.nix
+++ b/examples/checks-utils/flake.nix
@@ -7,22 +7,23 @@
     flake-utils.lib.eachDefaultSystem (system:
       let
         inherit (flake-utils.lib.check-utils system) isEqual hasKey;
-
-        testDataset = { key1 = "value1"; key2 = "value2"; key3 = "value3"; };
+        testDataset = { key1 = "value1"; key2 = 123; key3 = "some>value with^invalid&characters"; };
       in
       rec {
         checks = {
-          valid_key1 = isEqual testDataset.key1 "value1";
-          contains_key2 = hasKey testDataset "key2";
+          # Successful cases
+          success_isEqual = isEqual testDataset.key1 "value1";
+          success_hasKey = hasKey testDataset "key2";
 
-          failing_valid_key1 = isEqual testDataset.key1 "failing-data";
-          failing_contains_key2 = hasKey testDataset "failing-data";
+          # Failing cases
+          failure_isEqual = isEqual testDataset.key1 "failing-data";
+          failure_hasKey = hasKey testDataset "failing-data";
 
-          number_formatting_isEqual = isEqual testDataset.key1 123;
-          number_formatting_hasKey = hasKey testDataset 123;
+          # Formatting
+          formatting_number = isEqual testDataset.key2 123;
+          formatting_null = isEqual null null;
+          formatting_invalid_chars = isEqual testDataset.key3 "some>value with^invalid&characters";
 
-          null_formatting_key1 = isEqual testDataset.key1 null;
-          null_formatting_hasKey = hasKey testDataset null;
         };
       }
     );