diff --git a/blocks/html/block_html.php b/blocks/html/block_html.php
index 6ca71b30f1b..c60c118e9e3 100644
--- a/blocks/html/block_html.php
+++ b/blocks/html/block_html.php
@@ -104,7 +104,7 @@ class block_html extends block_base {
     function content_is_trusted() {
         global $SCRIPT;
 
-        if (!$context = context::instance_by_id($this->instance->parentcontextid)) {
+        if (!$context = context::instance_by_id($this->instance->parentcontextid, IGNORE_MISSING)) {
             return false;
         }
         //find out if this block is on the profile page
diff --git a/blocks/html/lib.php b/blocks/html/lib.php
index 93fdbb8c8e4..03d58ca27ce 100644
--- a/blocks/html/lib.php
+++ b/blocks/html/lib.php
@@ -53,7 +53,7 @@ function block_html_pluginfile($course, $birecord_or_cm, $context, $filearea, $a
         send_file_not_found();
     }
 
-    if ($parentcontext = context::instance_by_id($birecord_or_cm->parentcontextid)) {
+    if ($parentcontext = context::instance_by_id($birecord_or_cm->parentcontextid, IGNORE_MISSING)) {
         if ($parentcontext->contextlevel == CONTEXT_USER) {
             // force download on all personal pages including /my/
             //because we do not have reliable way to find out from where this is used
diff --git a/comment/locallib.php b/comment/locallib.php
index 25f907f4c16..c53fa801a20 100644
--- a/comment/locallib.php
+++ b/comment/locallib.php
@@ -114,7 +114,7 @@ class comment_manager {
      */
     private function setup_plugin($comment) {
         global $DB;
-        $this->context = context::instance_by_id($comment->contextid);
+        $this->context = context::instance_by_id($comment->contextid, IGNORE_MISSING);
         if (!$this->context) {
             return false;
         }
diff --git a/enrol/externallib.php b/enrol/externallib.php
index e669ca747f7..757362aa694 100644
--- a/enrol/externallib.php
+++ b/enrol/externallib.php
@@ -381,7 +381,7 @@ class core_role_external extends external_api {
 
         foreach ($params['assignments'] as $assignment) {
             // Ensure the current user is allowed to run this function in the enrolment context
-            $context = context::instance_by_id($assignment['contextid']);
+            $context = context::instance_by_id($assignment['contextid'], IGNORE_MISSING);
             self::validate_context($context);
             require_capability('moodle/role:assign', $context);
 
@@ -445,7 +445,7 @@ class core_role_external extends external_api {
 
         foreach ($params['unassignments'] as $unassignment) {
             // Ensure the current user is allowed to run this function in the unassignment context
-            $context = context::instance_by_id($unassignment['contextid']);
+            $context = context::instance_by_id($unassignment['contextid'], IGNORE_MISSING);
             self::validate_context($context);
             require_capability('moodle/role:assign', $context);
 
diff --git a/lib/filebrowser/file_info_context_course.php b/lib/filebrowser/file_info_context_course.php
index d1e703b7e9d..0f0816b15e9 100644
--- a/lib/filebrowser/file_info_context_course.php
+++ b/lib/filebrowser/file_info_context_course.php
@@ -401,7 +401,7 @@ class file_info_context_course extends file_info {
     public function get_parent() {
         //TODO: error checking if get_parent_contextid() returns false
         $pcid = get_parent_contextid($this->context);
-        $parent = context::instance_by_id($pcid);
+        $parent = context::instance_by_id($pcid, IGNORE_MISSING);
         return $this->browser->get_file_info($parent);
     }
 }
diff --git a/lib/filebrowser/file_info_context_coursecat.php b/lib/filebrowser/file_info_context_coursecat.php
index 47636e6ce06..9cab4502f25 100644
--- a/lib/filebrowser/file_info_context_coursecat.php
+++ b/lib/filebrowser/file_info_context_coursecat.php
@@ -195,7 +195,7 @@ class file_info_context_coursecat extends file_info {
      */
     public function get_parent() {
         $cid = get_parent_contextid($this->context);
-        $parent = context::instance_by_id($cid);
+        $parent = context::instance_by_id($cid, IGNORE_MISSING);
         return $this->browser->get_file_info($parent);
     }
 }
diff --git a/lib/filebrowser/file_info_context_module.php b/lib/filebrowser/file_info_context_module.php
index 363f6a0b82f..7e8ac7722ac 100644
--- a/lib/filebrowser/file_info_context_module.php
+++ b/lib/filebrowser/file_info_context_module.php
@@ -283,7 +283,7 @@ class file_info_context_module extends file_info {
      */
     public function get_parent() {
         $pcid = get_parent_contextid($this->context);
-        $parent = context::instance_by_id($pcid);
+        $parent = context::instance_by_id($pcid, IGNORE_MISSING);
         return $this->browser->get_file_info($parent);
     }
 }
diff --git a/lib/tests/accesslib_test.php b/lib/tests/accesslib_test.php
index b8535fd7c98..4542513ba49 100644
--- a/lib/tests/accesslib_test.php
+++ b/lib/tests/accesslib_test.php
@@ -2271,7 +2271,7 @@ class accesslib_testcase extends advanced_testcase {
 
         foreach ($DB->get_records('context') as $contextid=>$record) {
             $context = context::instance_by_id($contextid);
-            $this->assertSame(context::instance_by_id($contextid), $context);
+            $this->assertSame(context::instance_by_id($contextid, IGNORE_MISSING), $context);
             $this->assertSame(get_context_instance($record->contextlevel, $record->instanceid), $context);
             $this->assertSame(get_parent_contexts($context), $context->get_parent_context_ids());
             if ($context->id == SYSCONTEXTID) {
diff --git a/question/editlib.php b/question/editlib.php
index bb4633f4fd0..bb563f718f3 100644
--- a/question/editlib.php
+++ b/question/editlib.php
@@ -1717,7 +1717,7 @@ function question_get_display_preference($param, $default, $type, $thispageurl)
 function require_login_in_context($contextorid = null){
     global $DB, $CFG;
     if (!is_object($contextorid)){
-        $context = context::instance_by_id($contextorid);
+        $context = context::instance_by_id($contextorid, IGNORE_MISSING);
     } else {
         $context = $contextorid;
     }
diff --git a/question/type/questiontypebase.php b/question/type/questiontypebase.php
index 22226da6e3f..9b51a8b0043 100644
--- a/question/type/questiontypebase.php
+++ b/question/type/questiontypebase.php
@@ -1023,7 +1023,7 @@ class question_type {
     protected function get_context_by_category_id($category) {
         global $DB;
         $contextid = $DB->get_field('question_categories', 'contextid', array('id'=>$category));
-        $context = context::instance_by_id($contextid);
+        $context = context::instance_by_id($contextid, IGNORE_MISSING);
         return $context;
     }
 
diff --git a/repository/lib.php b/repository/lib.php
index 1a51e8eee1d..10a8d1c6573 100644
--- a/repository/lib.php
+++ b/repository/lib.php
@@ -1175,7 +1175,7 @@ abstract class repository {
             $fileinfo = null;
             $params = file_storage::unpack_reference($reference, true);
             if (is_array($params)) {
-                $context = context::instance_by_id($params['contextid']);
+                $context = context::instance_by_id($params['contextid'], IGNORE_MISSING);
                 if ($context) {
                     $browser = get_file_browser();
                     $fileinfo = $browser->get_file_info($context, $params['component'], $params['filearea'], $params['itemid'], $params['filepath'], $params['filename']);