diff --git a/polymorphic/query_translate.py b/polymorphic/query_translate.py
index 2974f4cb..7555ae5a 100644
--- a/polymorphic/query_translate.py
+++ b/polymorphic/query_translate.py
@@ -81,6 +81,25 @@ def tree_node_correct_field_specs(my_model, node):
     return potential_q_object
 
 
+def _deepcopy_q_object(q):
+    """
+    Make a deepcopy of a Q-object.
+    """
+    def _copy_child(child):
+        if isinstance(child, tuple):
+            return child  # tuples are immutable, no need to make a copy.
+        elif isinstance(child, Q):
+            return _deepcopy_q_object(child)
+        else:
+            raise RuntimeError("Unknown child type: %s", type(child))
+
+    obj = type(q).create(
+        connector=q.connector,
+        negated=q.negated,
+        children=[_copy_child(c) for c in q.children])
+    return obj
+
+
 def translate_polymorphic_filter_definitions_in_args(queryset_model, args, using=DEFAULT_DB_ALIAS):
     """
     Translate the non-keyword argument list for PolymorphicQuerySet.filter()
@@ -93,7 +112,7 @@ def translate_polymorphic_filter_definitions_in_args(queryset_model, args, using
     Returns: modified Q objects
     """
     return [
-        translate_polymorphic_Q_object(queryset_model, copy.deepcopy(q), using=using) for q in args
+        translate_polymorphic_Q_object(queryset_model, _deepcopy_q_object(q), using=using) for q in args
     ]