diff --git a/lib/grouplib.php b/lib/grouplib.php
index 826d0c481db..13e852df308 100644
--- a/lib/grouplib.php
+++ b/lib/grouplib.php
@@ -203,12 +203,18 @@ function groups_get_all_groups($courseid, $userid=0, $groupingid=0, $fields='g.*
     // aliased. If its something else we need to avoid the cache and run the query as who knows whats going on.
     $knownfields = true;
     if ($fields !== 'g.*') {
-        $fieldbits = explode(',', $fields);
-        foreach ($fieldbits as $bit) {
-            $bit = trim($bit);
-            if (strpos($bit, 'g.') !== 0 or stripos($bit, ' AS ') !== false) {
-                $knownfields = false;
-                break;
+        // Quickly check if the first field is no longer g.id as using the
+        // cache will return an array indexed differently than when expect
+        if (strpos($fields, 'g.*') !== 0 && strpos($fields, 'g.id') !== 0) {
+            $knownfields = false;
+        } else {
+            $fieldbits = explode(',', $fields);
+            foreach ($fieldbits as $bit) {
+                $bit = trim($bit);
+                if (strpos($bit, 'g.') !== 0 or stripos($bit, ' AS ') !== false) {
+                    $knownfields = false;
+                    break;
+                }
             }
         }
     }
diff --git a/lib/tests/grouplib_test.php b/lib/tests/grouplib_test.php
index ada661631d2..8f5fb5468a4 100644
--- a/lib/tests/grouplib_test.php
+++ b/lib/tests/grouplib_test.php
@@ -26,6 +26,10 @@
 
 defined('MOODLE_INTERNAL') || die();
 
+/**
+ * Unit tests for lib/grouplib.php
+ * @group core_group
+ */
 class core_grouplib_testcase extends advanced_testcase {
 
     public function test_groups_get_group_by_idnumber() {
@@ -404,6 +408,14 @@ class core_grouplib_testcase extends advanced_testcase {
         $this->assertNotContains($group2->id, $groupkeys);
         $this->assertContains($group3->id, $groupkeys);
         $this->assertContains($group4->id, $groupkeys);
+
+        // Test this function using an alternate column for the result index
+        $groups  = groups_get_all_groups($course->id, null, $grouping2->id, 'g.name, g.id');
+        $groupkeys = array_keys($groups);
+        $this->assertCount(2, $groups);
+        $this->assertNotContains($group3->id, $groupkeys);
+        $this->assertContains($group3->name, $groupkeys);
+        $this->assertEquals($group3->id, $groups[$group3->name]->id);
     }
 
     /**