diff --git a/cache/stores/file/lib.php b/cache/stores/file/lib.php
index 54dfe930c6c..607a4d22d93 100644
--- a/cache/stores/file/lib.php
+++ b/cache/stores/file/lib.php
@@ -195,6 +195,17 @@ class cachestore_file extends cache_store implements cache_is_key_aware, cache_i
         return $supported;
     }
 
+    /**
+     * Returns false as this store does not support multiple identifiers.
+     * (This optional function is a performance optimisation; it must be
+     * consistent with the value from get_supported_features.)
+     *
+     * @return bool False
+     */
+    public function supports_multiple_identifiers() {
+        return false;
+    }
+
     /**
      * Returns the supported modes as a combined int.
      *
diff --git a/cache/stores/memcache/lib.php b/cache/stores/memcache/lib.php
index 906b3556e49..f8a21b8a3ce 100644
--- a/cache/stores/memcache/lib.php
+++ b/cache/stores/memcache/lib.php
@@ -181,6 +181,17 @@ class cachestore_memcache extends cache_store implements cache_is_configurable {
         return self::SUPPORTS_NATIVE_TTL;
     }
 
+    /**
+     * Returns false as this store does not support multiple identifiers.
+     * (This optional function is a performance optimisation; it must be
+     * consistent with the value from get_supported_features.)
+     *
+     * @return bool False
+     */
+    public function supports_multiple_identifiers() {
+        return false;
+    }
+
     /**
      * Returns the supported modes as a combined int.
      *
diff --git a/cache/stores/memcached/lib.php b/cache/stores/memcached/lib.php
index 98d3955eacd..6e3834cce0f 100644
--- a/cache/stores/memcached/lib.php
+++ b/cache/stores/memcached/lib.php
@@ -205,6 +205,17 @@ class cachestore_memcached extends cache_store implements cache_is_configurable
         return self::SUPPORTS_NATIVE_TTL;
     }
 
+    /**
+     * Returns false as this store does not support multiple identifiers.
+     * (This optional function is a performance optimisation; it must be
+     * consistent with the value from get_supported_features.)
+     *
+     * @return bool False
+     */
+    public function supports_multiple_identifiers() {
+        return false;
+    }
+
     /**
      * Returns the supported modes as a combined int.
      *
diff --git a/cache/stores/session/lib.php b/cache/stores/session/lib.php
index 39ebbf32ff8..b2f77780b13 100644
--- a/cache/stores/session/lib.php
+++ b/cache/stores/session/lib.php
@@ -141,6 +141,17 @@ class cachestore_session extends session_data_store implements cache_is_key_awar
                self::IS_SEARCHABLE;
     }
 
+    /**
+     * Returns false as this store does not support multiple identifiers.
+     * (This optional function is a performance optimisation; it must be
+     * consistent with the value from get_supported_features.)
+     *
+     * @return bool False
+     */
+    public function supports_multiple_identifiers() {
+        return false;
+    }
+
     /**
      * Returns the supported modes as a combined int.
      *
diff --git a/cache/stores/static/lib.php b/cache/stores/static/lib.php
index cc74f7409ba..405474abc4c 100644
--- a/cache/stores/static/lib.php
+++ b/cache/stores/static/lib.php
@@ -136,6 +136,17 @@ class cachestore_static extends static_data_store implements cache_is_key_aware
                self::SUPPORTS_NATIVE_TTL;
     }
 
+    /**
+     * Returns false as this store does not support multiple identifiers.
+     * (This optional function is a performance optimisation; it must be
+     * consistent with the value from get_supported_features.)
+     *
+     * @return bool False
+     */
+    public function supports_multiple_identifiers() {
+        return false;
+    }
+
     /**
      * Returns the supported modes as a combined int.
      *