diff --git a/passphrase_cache.hh b/passphrase_cache.hh
index f47490e..4a82a3c 100644
--- a/passphrase_cache.hh
+++ b/passphrase_cache.hh
@@ -35,6 +35,7 @@ namespace pEp {
         ~PassphraseCache() { }
         PassphraseCache(const PassphraseCache& second) : _cache(second._cache),
                 _max_size(second._max_size), _timeout(second._timeout) { }
+        PassphraseCache operator=(const PassphraseCache& second) { return second; }
 
         // adding a passphrase to the cache, which will timeout
 
diff --git a/test/test_passphrase_cache.cc b/test/test_passphrase_cache.cc
index 9879d99..05ce33a 100644
--- a/test/test_passphrase_cache.cc
+++ b/test/test_passphrase_cache.cc
@@ -59,6 +59,8 @@ int main()
     status = cache.api(api_test2, session, 23, str, bytes, sl);
     assert(status == PEP_STATUS_OK);
 
+    pEp::PassphraseCache _cache = cache;
+
     ::release(session);
     return 0;
 }