diff --git a/cachalot/utils.py b/cachalot/utils.py
index 3113c6b..72792fc 100644
--- a/cachalot/utils.py
+++ b/cachalot/utils.py
@@ -9,8 +9,10 @@ from uuid import UUID
 
 from django import VERSION as django_version
 from django.db import connections
+from django.db.models.expressions import RawSQL
 from django.db.models.sql import Query
-from django.db.models.sql.where import ExtraWhere, SubqueryConstraint
+from django.db.models.sql.where import (
+    ExtraWhere, SubqueryConstraint, WhereNode)
 from django.utils.module_loading import import_string
 from django.utils.six import text_type, binary_type
 
@@ -22,6 +24,10 @@ class UncachableQuery(Exception):
     pass
 
 
+class IsRawQuery(Exception):
+    pass
+
+
 TUPLE_OR_LIST = {tuple, list}
 
 CACHABLE_PARAM_TYPES = {
@@ -112,25 +118,30 @@ def _get_tables_from_sql(connection, lowercased_sql):
 
 def _find_subqueries(children):
     for child in children:
-        if child.__class__ is SubqueryConstraint:
+        child_class = child.__class__
+        if child_class is WhereNode:
+            for grand_child in _find_subqueries(child.children):
+                yield grand_child
+        elif child_class is SubqueryConstraint:
             if child.query_object.__class__ is Query:
                 yield child.query_object
             else:
                 yield child.query_object.query
+        elif child_class is ExtraWhere:
+            raise IsRawQuery
         else:
             rhs = None
             if hasattr(child, 'rhs'):
                 rhs = child.rhs
             rhs_class = rhs.__class__
+            if rhs_class is RawSQL:
+                raise IsRawQuery
             if rhs_class is Query:
                 yield rhs
             elif hasattr(rhs, 'query'):
                 yield rhs.query
             elif rhs_class in UNCACHABLE_FUNCS:
                 raise UncachableQuery
-        if hasattr(child, 'children'):
-            for grand_child in _find_subqueries(child.children):
-                yield grand_child
 
 
 def is_cachable(table):
@@ -161,16 +172,16 @@ def _get_tables(db_alias, query):
             and not cachalot_settings.CACHALOT_CACHE_RANDOM):
         raise UncachableQuery
 
-    if query.extra_select or getattr(query, 'subquery', False) \
-            or any(c.__class__ is ExtraWhere for c in query.where.children):
-        sql = query.get_compiler(db_alias).as_sql()[0].lower()
-        tables = _get_tables_from_sql(connections[db_alias], sql)
-    else:
+    try:
+        if query.extra_select or getattr(query, 'subquery', False):
+            raise IsRawQuery
         tables = set(query.table_map)
         tables.add(query.get_meta().db_table)
-        subquery_constraints = _find_subqueries(query.where.children)
-        for subquery in subquery_constraints:
+        for subquery in _find_subqueries(query.where.children):
             tables.update(_get_tables(db_alias, subquery))
+    except IsRawQuery:
+        sql = query.get_compiler(db_alias).as_sql()[0].lower()
+        tables = _get_tables_from_sql(connections[db_alias], sql)
 
     if not are_all_cachable(tables):
         raise UncachableQuery