diff --git a/mod/quiz/report/overview/report.php b/mod/quiz/report/overview/report.php
index 5ba30b8015b..c80453b8f3e 100644
--- a/mod/quiz/report/overview/report.php
+++ b/mod/quiz/report/overview/report.php
@@ -634,11 +634,11 @@ class quiz_overview_report extends quiz_default_report {
                 // Ensure the attempt exists, and belongs to this quiz. If not skip.
                 continue;
             }
-            if ($allowed && !array_key_exists($attempt->userid, $allowed)) {
+            if ($allowed && !in_array($attempt->userid, $allowed)) {
                 // Ensure the attempt belongs to a student included in the report. If not skip.
                 continue;
             }
-            if ($groupstudents && !array_key_exists($attempt->userid, $groupstudents)) {
+            if ($groupstudents && !in_array($attempt->userid, $groupstudents)) {
                 // Additional check in groups mode.
                 continue;
             }
diff --git a/mod/quiz/report/responses/report.php b/mod/quiz/report/responses/report.php
index b296fd68185..1c7fe7579b4 100644
--- a/mod/quiz/report/responses/report.php
+++ b/mod/quiz/report/responses/report.php
@@ -114,11 +114,11 @@ class quiz_responses_report extends quiz_default_report {
                     // Ensure the attempt exists, and belongs to this quiz. If not skip.
                     continue;
                 }
-                if ($attemptsmode != QUIZ_REPORT_ATTEMPTS_ALL && !array_key_exists($attempt->userid, $students)) {
+                if ($attemptsmode != QUIZ_REPORT_ATTEMPTS_ALL && !in_array($attempt->userid, $students)) {
                     // Ensure the attempt belongs to a student included in the report. If not skip.
                     continue;
                 }
-                if ($groupstudents && !array_key_exists($attempt->userid, $groupstudents)) {
+                if ($groupstudents && !in_array($attempt->userid, $groupstudents)) {
                     // Additional check in groups mode.
                     continue;
                 }