diff --git a/mod/quiz/report/reportlib.php b/mod/quiz/report/reportlib.php
index ff17ccfcafb..9919d8c7c4c 100644
--- a/mod/quiz/report/reportlib.php
+++ b/mod/quiz/report/reportlib.php
@@ -248,6 +248,14 @@ ORDER BY
     $data[$bands - 1] += $data[$bands];
     unset($data[$bands]);
 
+    // See MDL-60632. When a quiz participant achieves an overall negative grade the chart fails to render.
+    foreach ($data as $databand => $datanum) {
+        if ($databand < 0) {
+            $data["0"] += $datanum; // Add to band 0.
+            unset($data[$databand]); // Remove entry below 0.
+        }
+    }
+
     return $data;
 }
 
diff --git a/mod/quiz/tests/reportlib_test.php b/mod/quiz/tests/reportlib_test.php
index 69432ff0eb9..289eb7f8ea6 100644
--- a/mod/quiz/tests/reportlib_test.php
+++ b/mod/quiz/tests/reportlib_test.php
@@ -158,4 +158,37 @@ class reportlib_test extends \advanced_testcase {
         $bestattempt = reset($bestattempt);
         $this->assertEquals(2, $bestattempt->attempt);
     }
+
+    public function test_quiz_results_never_below_zero() {
+        global $DB;
+        $this->resetAfterTest();
+
+        $quizid = 7;
+        $fakegrade = new \stdClass();
+        $fakegrade->quiz = $quizid;
+
+        // Have 5 test grades.
+        $fakegrade->userid = 10;
+        $fakegrade->grade = 6.66667;
+        $DB->insert_record('quiz_grades', $fakegrade);
+
+        $fakegrade->userid = 11;
+        $fakegrade->grade = -2.86;
+        $DB->insert_record('quiz_grades', $fakegrade);
+
+        $fakegrade->userid = 12;
+        $fakegrade->grade = 10.0;
+        $DB->insert_record('quiz_grades', $fakegrade);
+
+        $fakegrade->userid = 13;
+        $fakegrade->grade = -5.0;
+        $DB->insert_record('quiz_grades', $fakegrade);
+
+        $fakegrade->userid = 14;
+        $fakegrade->grade = 33.33333;
+        $DB->insert_record('quiz_grades', $fakegrade);
+
+        $data = quiz_report_grade_bands(5, 20, $quizid);
+        $this->assertGreaterThanOrEqual(0, min(array_keys($data)));
+    }
 }