diff --git a/course/moodleform_mod.php b/course/moodleform_mod.php
index cad2bf879e5..0d47d96b604 100644
--- a/course/moodleform_mod.php
+++ b/course/moodleform_mod.php
@@ -492,8 +492,16 @@ abstract class moodleform_mod extends moodleform {
                     $validategradepass = true;
                 }
 
-                // Confirm gradepass is a valid non-zero value.
-                if ($validategradepass && (!isset($data[$gradepassfieldname]) || grade_floatval($data[$gradepassfieldname]) == 0)) {
+                // We need to make all the validations related with $gradepassfieldname
+                // with them being correct floats, keeping the originals unmodified for
+                // later validations / showing the form back...
+                // TODO: Note that once MDL-73994 is fixed we'll have to re-visit this and
+                // adapt the code below to the new values arriving here, without forgetting
+                // the special case of empties and nulls.
+                $gradepass = isset($data[$gradepassfieldname]) ? unformat_float($data[$gradepassfieldname]) : null;
+
+                // Confirm gradepass is a valid non-empty (null or zero) value.
+                if ($validategradepass && (is_null($gradepass) || $gradepass == 0)) {
                     $errors['completionpassgrade'] = get_string(
                         'activitygradetopassnotset',
                         'completion'
@@ -959,10 +967,9 @@ abstract class moodleform_mod extends moodleform {
         }
 
         // Grade to pass.
-        $mform->addElement('text', $gradepassfieldname, get_string('gradepass', 'grades'));
+        $mform->addElement('float', $gradepassfieldname, get_string('gradepass', 'grades'));
         $mform->addHelpButton($gradepassfieldname, 'gradepass', 'grades');
         $mform->setDefault($gradepassfieldname, '');
-        $mform->setType($gradepassfieldname, PARAM_RAW);
         $mform->hideIf($gradepassfieldname, $assessedfieldname, 'eq', '0');
         $mform->hideIf($gradepassfieldname, "{$scalefieldname}[modgrade_type]", 'eq', 'none');
     }
@@ -1136,10 +1143,9 @@ abstract class moodleform_mod extends moodleform {
             }
 
             // Grade to pass.
-            $mform->addElement('text', $gradepassfieldname, get_string($gradepassfieldname, 'grades'));
+            $mform->addElement('float', $gradepassfieldname, get_string($gradepassfieldname, 'grades'));
             $mform->addHelpButton($gradepassfieldname, $gradepassfieldname, 'grades');
             $mform->setDefault($gradepassfieldname, '');
-            $mform->setType($gradepassfieldname, PARAM_RAW);
             $mform->hideIf($gradepassfieldname, "{$gradefieldname}[modgrade_type]", 'eq', 'none');
         }
     }
diff --git a/lib/gradelib.php b/lib/gradelib.php
index 71cdc236595..72d13e40564 100644
--- a/lib/gradelib.php
+++ b/lib/gradelib.php
@@ -1586,14 +1586,14 @@ function grade_course_reset($courseid) {
 }
 
 /**
- * Convert a number to 5 decimal point float, an empty string or a null db compatible format
+ * Convert a number to 5 decimal point float, null db compatible format
  * (we need this to decide if db value changed)
  *
  * @param float|null $number The number to convert
  * @return float|null float or null
  */
 function grade_floatval(?float $number) {
-    if (is_null($number) or $number === '') {
+    if (is_null($number)) {
         return null;
     }
     // we must round to 5 digits to get the same precision as in 10,5 db fields
diff --git a/mod/quiz/tests/behat/completion_condition_passing_grade.feature b/mod/quiz/tests/behat/completion_condition_passing_grade.feature
index b021ca18d50..ff9bbfae821 100644
--- a/mod/quiz/tests/behat/completion_condition_passing_grade.feature
+++ b/mod/quiz/tests/behat/completion_condition_passing_grade.feature
@@ -54,3 +54,36 @@ Feature: Set a quiz to be marked complete when the student passes
     And I navigate to "Reports" in current page administration
     And I click on "Activity completion" "link"
     And "Completed" "icon" should exist in the "Student 1" "table_row"
+
+  Scenario Outline: Verify that gradepass, together with completionpassgrade are validated correctly
+    Given the following "language customisations" exist:
+      | component       | stringid | value    |
+      | core_langconfig | decsep   | <decsep> |
+    And the following "activity" exist:
+      | activity | name                             | course | idnumber | gradepass  | completion | completionpassgrade   |
+      | quiz     | Oh, grades, passgrades and floats| C1     | ohgrades | <gradepass>| 2          | <completionpassgrade> |
+    When  I am on the "ohgrades" "quiz activity editing" page logged in as "teacher1"
+    And I expand all fieldsets
+    And I set the field "Grade to pass" to "<gradepass>"
+    And I set the field "completionusegrade" to "1"
+    And I set the field "completionpassgrade" to "<completionpassgrade>"
+    And I press "Save and display"
+    Then I should see "<seen>"
+    And I should not see "<notseen>"
+
+    Examples:
+      | gradepass | completionpassgrade | decsep | seen                  | notseen          | outcome        |
+      |           | 0                   | .      | method: Highest       | Save and display | ok             |
+      |           | 1                   | .      | does not have a valid | method: Highest  | completion-err |
+      | 0         | 0                   | .      | method: Highest       | Save and display | ok             |
+      | 0         | 1                   | .      | does not have a valid | method: Highest  | completion-err |
+      | aaa       | 0                   | .      | must enter a number   | method: Highest  | number-err     |
+      | aaa       | 1                   | .      | must enter a number   | method: Highest  | number-err     |
+      | 200       | 0                   | .      | can not be greater    | method: Highest  | grade-big-err  |
+      | 200       | 1                   | .      | can not be greater    | method: Highest  | grade-big-err  |
+      | 5.55      | 0                   | .      | 5.55 out of 100       | Save and display | ok             |
+      | 5.55      | 1                   | .      | 5.55 out of 100       | Save and display | ok             |
+      | 5#55      | 0                   | .      | must enter a number   | method: Highest  | number-err     |
+      | 5#55      | 1                   | .      | must enter a number   | method: Highest  | number-err     |
+      | 5#55      | 0                   | #      | 5#55 out of 100       | Save and display | ok             |
+      | 5#55      | 1                   | #      | 5#55 out of 100       | Save and display | ok             |