diff --git a/tests/test_mapper_no_duplicate_keys.py b/tests/test_mapper_no_duplicate_keys.py
index ff474dbe82..950db478b0 100644
--- a/tests/test_mapper_no_duplicate_keys.py
+++ b/tests/test_mapper_no_duplicate_keys.py
@@ -9,7 +9,6 @@ We inspect the source with ``ast`` to ensure there are no duplicates.
 
 import ast
 import os
-from collections import Counter
 
 MAPPER_PATH = os.path.join(os.path.dirname(__file__), os.pardir, "unsloth", "models", "mapper.py")
 
@@ -22,18 +21,27 @@ def _duplicate_int_to_float_keys():
         if not isinstance(node, ast.Assign):
             continue
         for target in node.targets:
-            # The name is mangled at class scope, but at module scope it is the
-            # plain ``__INT_TO_FLOAT_MAPPER`` identifier.
+            # ``ast.parse`` stops before code generation, so the identifier is
+            # never private-name-mangled and reads exactly as written.
             if isinstance(target, ast.Name) and target.id == "__INT_TO_FLOAT_MAPPER":
                 if not isinstance(node.value, ast.Dict):
                     continue
-                keys = [
-                    k.value
-                    for k in node.value.keys
-                    if isinstance(k, ast.Constant) and isinstance(k.value, str)
-                ]
-                counts = Counter(keys)
-                return {key: n for key, n in counts.items() if n > 1}
+                # An entry may nest a per-precision dict ("16" / "8") that
+                # mapper.py reads directly, so every dict literal in the
+                # registry is checked. Keys are counted per dict, since "16"
+                # and "8" legitimately repeat across sibling entries.
+                duplicates = {}
+                for mapping in ast.walk(node.value):
+                    if not isinstance(mapping, ast.Dict):
+                        continue
+                    seen = set()
+                    for k in mapping.keys:
+                        if not (isinstance(k, ast.Constant) and isinstance(k.value, str)):
+                            continue
+                        if k.value in seen:
+                            duplicates.setdefault(k.value, []).append(k.lineno)
+                        seen.add(k.value)
+                return duplicates
     raise AssertionError("Could not find the __INT_TO_FLOAT_MAPPER dict literal in mapper.py")
 
 
@@ -42,5 +50,5 @@ def test_int_to_float_mapper_has_no_duplicate_keys():
     assert not duplicates, (
         "Duplicate keys in __INT_TO_FLOAT_MAPPER silently overwrite earlier "
         "entries and corrupt model resolution. Remove the redundant "
-        f"literal(s): {duplicates}"
+        f"literal(s), key -> line number(s) in mapper.py: {duplicates}"
     )