diff --git a/cache/stores/memcache/tests/memcache_test.php b/cache/stores/memcache/tests/memcache_test.php
index 05ece1b4bc8e6..4e3c2aa9e4354 100644
--- a/cache/stores/memcache/tests/memcache_test.php
+++ b/cache/stores/memcache/tests/memcache_test.php
@@ -67,6 +67,10 @@ public function test_valid_keys() {
         $definition = cache_definition::load_adhoc(cache_store::MODE_APPLICATION, 'cachestore_memcache', 'phpunit_test');
         $instance = cachestore_memcache::initialise_test_instance($definition);
 
+        if (!$instance) { // Something prevented memcache store to be inited (extension, TEST_CACHESTORE_MEMCACHE_TESTSERVERS...).
+            $this->markTestSkipped();
+        }
+
         $keys = array(
             // Alphanumeric.
             'abc', 'ABC', '123', 'aB1', '1aB',
@@ -86,4 +90,4 @@ public function test_valid_keys() {
             $this->assertEquals($key, $value);
         }
     }
-}
\ No newline at end of file
+}
diff --git a/cache/stores/memcached/tests/memcached_test.php b/cache/stores/memcached/tests/memcached_test.php
index 85a8e4a91cba5..80a918a38c7a3 100644
--- a/cache/stores/memcached/tests/memcached_test.php
+++ b/cache/stores/memcached/tests/memcached_test.php
@@ -67,6 +67,10 @@ public function test_valid_keys() {
         $definition = cache_definition::load_adhoc(cache_store::MODE_APPLICATION, 'cachestore_memcached', 'phpunit_test');
         $instance = cachestore_memcached::initialise_test_instance($definition);
 
+        if (!$instance) { // Something prevented memcached store to be inited (extension, TEST_CACHESTORE_MEMCACHED_TESTSERVERS...).
+            $this->markTestSkipped();
+        }
+
         $keys = array(
             // Alphanumeric.
             'abc', 'ABC', '123', 'aB1', '1aB',
@@ -86,4 +90,4 @@ public function test_valid_keys() {
             $this->assertEquals($key, $value);
         }
     }
-}
\ No newline at end of file
+}