diff --git a/src/library/persistent_context_cache.cpp b/src/library/persistent_context_cache.cpp
index 9ce357cbe8..bad1dff7fa 100644
--- a/src/library/persistent_context_cache.cpp
+++ b/src/library/persistent_context_cache.cpp
@@ -9,7 +9,7 @@ Author: Leonardo de Moura
 #include "library/context_cache.h"
 
 namespace lean {
-typedef std::pair<unique_id, std::unique_ptr<context_cache>> unique_id_context_cache_pair;
+typedef std::pair<unique_id, std::unique_ptr<abstract_context_cache>> unique_id_context_cache_pair;
 
 MK_THREAD_LOCAL_GET_DEF(unique_id_context_cache_pair, get_unique_id_context_cache_pair);
 
diff --git a/src/library/persistent_context_cache.h b/src/library/persistent_context_cache.h
index 0f35381c3d..bd6d2053cc 100644
--- a/src/library/persistent_context_cache.h
+++ b/src/library/persistent_context_cache.h
@@ -25,8 +25,8 @@ typedef unique_id context_cache_id;
    See comment at abstract_context_cache for more details.
 */
 class persistent_context_cache : public abstract_context_cache {
-    context_cache_id               m_id;
-    std::unique_ptr<context_cache> m_cache_ptr;
+    context_cache_id                        m_id;
+    std::unique_ptr<abstract_context_cache> m_cache_ptr;
 public:
     persistent_context_cache(context_cache_id, options const &);
     virtual ~persistent_context_cache();