diff --git a/www/_include.php b/www/_include.php
index 6b1c60f70d57357dc88fba711be263a06bc50704..90f15ef48e5eb553675db2081a5b02148ed2da33 100644
--- a/www/_include.php
+++ b/www/_include.php
@@ -33,11 +33,25 @@ ini_set('include_path', $path);
 
 
 /**
- * If you have troubles with the ini_set method above, in example because you run on a hosted
- * web hotel where this method is not allowed to call, comment out the three lines above, and instead
- * uncomment this line:
+ * Class which should print a warning every time a reference to $SIMPLESAML_INCPREFIX is made.
  */
-//$SIMPLESAML_INCPREFIX = $path_extra . '/';
+class SimpleSAML_IncPrefixWarn {
+
+	/**
+	 * Print a warning, as a call to this function means that $SIMPLESAML_INCPREFIX is referenced.
+	 *
+	 * @return A blank string.
+	 */
+	function __toString() {
+		$backtrace = debug_backtrace();
+		$where = $backtrace[0]['file'] . ':' . $backtrace[0]['line'];
+		error_log('Deprecated $SIMPLESAML_INCPREFIX still in use at ' . $where .
+			'. The simpleSAMLphp library now uses an autoloader.');
+		return '';
+	}
+}
+/* Set the $SIMPLESAML_INCPREFIX to a reference to the class. */
+$SIMPLESAML_INCPREFIX = new SimpleSAML_IncPrefixWarn();
 
 
 $configdir = dirname(dirname(__FILE__)) . '/config';