diff --git a/admin/cli/install.php b/admin/cli/install.php
index 704be90b409b5..5578213dc2120 100644
--- a/admin/cli/install.php
+++ b/admin/cli/install.php
@@ -151,7 +151,6 @@
 $CFG->running_installer    = true;
 $CFG->early_install_lang   = true;
 $CFG->ostype               = (stristr(PHP_OS, 'win') && !stristr(PHP_OS, 'darwin')) ? 'WINDOWS' : 'UNIX';
-$CFG->developerdebug       = true;
 $CFG->dboptions            = array();
 
 $parts = explode('/', str_replace('\\', '/', dirname(dirname(__FILE__))));
diff --git a/cache/classes/helper.php b/cache/classes/helper.php
index a6de07a0430fe..6f30b4b2bf990 100644
--- a/cache/classes/helper.php
+++ b/cache/classes/helper.php
@@ -518,9 +518,8 @@ public static function get_definition_name($definition) {
      * @return string
      */
     public static function hash_key($key, cache_definition $definition) {
-        global $CFG;
         if ($definition->uses_simple_keys()) {
-            if ($CFG->developerdebug && preg_match('#[^a-zA-Z0-9_]#', $key)) {
+            if (debugging() && preg_match('#[^a-zA-Z0-9_]#', $key)) {
                 throw new coding_exception('Cache definition '.$definition->get_id().' requires simple keys. Invalid key provided.', $key);
             }
             // We put the key first so that we can be sure the start of the key changes.
diff --git a/install.php b/install.php
index b3400366a312d..d71e7a584632f 100644
--- a/install.php
+++ b/install.php
@@ -175,7 +175,6 @@
 $CFG->running_installer    = true;
 $CFG->early_install_lang   = true;
 $CFG->ostype               = (stristr(PHP_OS, 'win') && !stristr(PHP_OS, 'darwin')) ? 'WINDOWS' : 'UNIX';
-$CFG->developerdebug       = true;
 
 // Require all needed libs
 require_once($CFG->libdir.'/setuplib.php');
diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index bc3a8ecc4d3d0..a7e577b38cc49 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -7579,7 +7579,7 @@ function get_string($identifier, $component = '', $a = NULL, $lazyload = false)
         return new lang_string($identifier, $component, $a);
     }
 
-    if ($CFG->developerdebug && clean_param($identifier, PARAM_STRINGID) === '') {
+    if (debugging('', DEBUG_DEVELOPER) && clean_param($identifier, PARAM_STRINGID) === '') {
         throw new coding_exception('Invalid string identifier. The identifier cannot be empty. Please fix your get_string() call.');
     }
 
@@ -11376,7 +11376,6 @@ class lang_string {
      * @param string $lang The language to use when processing the string.
      */
     public function __construct($identifier, $component = '', $a = null, $lang = null) {
-        global $CFG;
         if (empty($component)) {
             $component = 'moodle';
         }
@@ -11414,7 +11413,7 @@ public function __construct($identifier, $component = '', $a = null, $lang = nul
             }
         }
 
-        if ($CFG->developerdebug) {
+        if (debugging(false, DEBUG_DEVELOPER)) {
             if (clean_param($this->identifier, PARAM_STRINGID) == '') {
                 throw new coding_exception('Invalid string identifier. Most probably some illegal character is part of the string identifier. Please check your string definition');
             }
diff --git a/lib/setup.php b/lib/setup.php
index 4625988a87789..0b9cbd2f40a1d 100644
--- a/lib/setup.php
+++ b/lib/setup.php
@@ -54,13 +54,6 @@
     }
 }
 
-// The 'developerdebug' value is relied upon by various functions, so set it
-// immediately (before debugging value is actually known).
-if (!isset($CFG->developerdebug)) {
-    $tempdeveloperdebug = true;
-    $CFG->developerdebug = false;
-}
-
 // We can detect real dirroot path reliably since PHP 4.0.2,
 // it can not be anything else, there is no point in having this in config.php
 $CFG->dirroot = dirname(dirname(__FILE__));
@@ -619,9 +612,6 @@
 unset($originalconfigdebug);
 unset($originaldatabasedebug);
 error_reporting($CFG->debug);
-if (!empty($tempdeveloperdebug)) {
-    $CFG->developerdebug = debugging('', DEBUG_DEVELOPER);
-}
 
 // find out if PHP configured to display warnings,
 // this is a security problem because some moodle scripts may
diff --git a/lib/upgrade.txt b/lib/upgrade.txt
index 6b1eed1f3ee47..e33f0c835488c 100644
--- a/lib/upgrade.txt
+++ b/lib/upgrade.txt
@@ -69,9 +69,6 @@ information provided here is intended especially for developers.
   uninstall tool is returned. Unless the plugin type needs extra steps that can't be handled by
   plugininfo_xxx::uninstall() method or xmldb_xxx_uninstall() function, this default URL should
   satisfy all plugin types.
-* New pattern 'if ($CFG->developerdebug) {}' can be used when checking whether to carry
-  out additional sanity checks - faster than debugging('', DEBUG_DEVELOPER), but
-  that still works too.
 
 Database (DML) layer:
 * $DB->sql_empty() is deprecated, you have to use sql parameters with empty values instead,