diff --git a/mod/quiz/report/overview/overviewgraph.php b/mod/quiz/report/overview/overviewgraph.php
index 4efa315014b..aeccfa1a78e 100644
--- a/mod/quiz/report/overview/overviewgraph.php
+++ b/mod/quiz/report/overview/overviewgraph.php
@@ -90,7 +90,9 @@ while ($bands > 20 || $bands <= 10) {
     }
 }
 
-$bands = ceil($bands);
+// See MDL-34589. Using doubles as array keys causes problems in PHP 5.4,
+// hence the explicit cast to int.
+$bands = (int) ceil($bands);
 $bandwidth = $quiz->grade / $bands;
 $bandlabels = array();
 for ($i = 1; $i <= $bands; $i++) {
diff --git a/mod/quiz/report/reportlib.php b/mod/quiz/report/reportlib.php
index 8154d4dfd4a..0e7001b5783 100644
--- a/mod/quiz/report/reportlib.php
+++ b/mod/quiz/report/reportlib.php
@@ -190,6 +190,11 @@ function quiz_report_qm_filter_select($quiz, $quizattemptsalias = 'quiza') {
  */
 function quiz_report_grade_bands($bandwidth, $bands, $quizid, $userids = array()) {
     global $DB;
+    if (!is_int($bands)) {
+        debugging('$bands passed to quiz_report_grade_bands must be an integer. (' .
+                gettype($bands) . ' passed.)', DEBUG_DEVELOPER);
+        $bands = (int) $bands;
+    }
 
     if ($userids) {
         list($usql, $params) = $DB->get_in_or_equal($userids, SQL_PARAMS_NAMED, 'u');
@@ -218,8 +223,8 @@ ORDER BY
 
     $data = $DB->get_records_sql_menu($sql, $params);
 
-    //need to create array elements with values 0 at indexes where there is no element
-    $data =  $data + array_fill(0, $bands+1, 0);
+    // We need to create array elements with values 0 at indexes where there is no element.
+    $data =  $data + array_fill(0, $bands + 1, 0);
     ksort($data);
 
     //place the maximum (prefect grade) into the last band i.e. make last