diff --git a/mod/quiz/questiontypes/numerical/questiontype.php b/mod/quiz/questiontypes/numerical/questiontype.php
index 5afbd93d7030b..b6e519da1c23f 100644
--- a/mod/quiz/questiontypes/numerical/questiontype.php
+++ b/mod/quiz/questiontypes/numerical/questiontype.php
@@ -163,7 +163,7 @@ function grade_response($question, $nameprefix, $addedanswercondition='') {
                     unset($responsenum); // Answer is not numeric
                 }
             } else if (ereg(
-                    '^(([0-9]+(\\.[0-9]*)?|[.][0-9]+)([eE][-+]?[0-9]+)?)([^0-9].*)?$',
+                    '^([+-]?([0-9]+(\\.[0-9]*)?|[.][0-9]+)([eE][-+]?[0-9]+)?)([^0-9].*)?$',
                     $responsenum, $responseparts)) {
                 $responsenum = (float)$responseparts[1];
                 if ($responseparts[5]) {