diff --git a/drupal_apc_cache.inc b/drupal_apc_cache.inc
index e06178d..1deadc9 100644
--- a/drupal_apc_cache.inc
+++ b/drupal_apc_cache.inc
@@ -246,4 +246,9 @@ class DrupalAPCCache implements DrupalCacheInterface {
       }
     }
   }
+
+  function isEmpty() {
+    // We do not know so err on the safe side?
+    return FALSE;
+  }
 }