diff --git a/jsonschema/_utils.py b/jsonschema/_utils.py
index ceb880198..90aa689f3 100644
--- a/jsonschema/_utils.py
+++ b/jsonschema/_utils.py
@@ -184,29 +184,48 @@ def unbool(element, true=object(), false=object()):
     return element
 
 
+def unbool_nested(element):
+    """
+    Iterative implementation of breadth-first search for nested unbooling
+    """
+
+    if not isinstance(element, (list, dict)):
+        return unbool(element)
+
+    result = [] if isinstance(element, list) else {}
+    stack = [(element, result)]
+    while stack:
+        element, new = stack.pop()
+        items = enumerate(element) if isinstance(element, list) else element.items()
+        for key, item in items:
+            if not isinstance(item, (list, dict)):
+                x = unbool(item)
+            else:
+                sub = [] if isinstance(item, list) else {}
+                x = sub
+                stack.append((item, sub))
+
+            if isinstance(new, list):
+                new.append(x)
+            else:
+                new[key] = x
+    return result
+
+
 def uniq(container):
     """
     Check if all of a container's elements are unique.
 
-    Successively tries first to rely that the elements are hashable, then
-    falls back on them being sortable, and finally falls back on brute
-    force.
+    Successively tries first to rely that the elements are hashable. If not, it goes to brute force.
     """
 
     try:
         return len(set(unbool(i) for i in container)) == len(container)
     except TypeError:
-        try:
-            sort = sorted(unbool(i) for i in container)
-            sliced = itertools.islice(sort, 1, None)
-            for i, j in zip(sort, sliced):
-                if i == j:
-                    return False
-        except (NotImplementedError, TypeError):
-            seen = []
-            for e in container:
-                e = unbool(e)
-                if e in seen:
-                    return False
-                seen.append(e)
+        seen = []
+        for element in container:
+            element = unbool_nested(element)
+            if element in seen:
+                return False
+            seen.append(element)
     return True