diff --git a/reportbuilder/classes/local/aggregation/avg.php b/reportbuilder/classes/local/aggregation/avg.php
index 16ff16a9c4b..57d73b13a2b 100644
--- a/reportbuilder/classes/local/aggregation/avg.php
+++ b/reportbuilder/classes/local/aggregation/avg.php
@@ -70,9 +70,10 @@ class avg extends base {
      * @param mixed $value
      * @param array $values
      * @param array $callbacks
-     * @return mixed
+     * @param int $columntype
+     * @return string
      */
-    public static function format_value($value, array $values, array $callbacks) {
+    public static function format_value($value, array $values, array $callbacks, int $columntype): string {
         return format_float((float) reset($values), 1);
     }
 }
diff --git a/reportbuilder/classes/local/aggregation/base.php b/reportbuilder/classes/local/aggregation/base.php
index f175133970b..6ddb1316fa8 100644
--- a/reportbuilder/classes/local/aggregation/base.php
+++ b/reportbuilder/classes/local/aggregation/base.php
@@ -126,9 +126,10 @@ abstract class base {
      * @param mixed $value
      * @param array $values
      * @param array $callbacks Array of column callbacks, {@see column::add_callback} for definition
+     * @param int $columntype The original type of the column, to ensure it is preserved for callbacks
      * @return mixed
      */
-    public static function format_value($value, array $values, array $callbacks) {
+    public static function format_value($value, array $values, array $callbacks, int $columntype) {
         foreach ($callbacks as $callback) {
             [$callable, $arguments] = $callback;
             $value = ($callable)($value, (object) $values, $arguments);
diff --git a/reportbuilder/classes/local/aggregation/count.php b/reportbuilder/classes/local/aggregation/count.php
index e3bb2108088..e93d400c413 100644
--- a/reportbuilder/classes/local/aggregation/count.php
+++ b/reportbuilder/classes/local/aggregation/count.php
@@ -72,9 +72,10 @@ class count extends base {
      * @param mixed $value
      * @param array $values
      * @param array $callbacks
-     * @return mixed
+     * @param int $columntype
+     * @return int
      */
-    public static function format_value($value, array $values, array $callbacks) {
+    public static function format_value($value, array $values, array $callbacks, int $columntype): int {
         return (int) reset($values);
     }
 }
diff --git a/reportbuilder/classes/local/aggregation/countdistinct.php b/reportbuilder/classes/local/aggregation/countdistinct.php
index ffcd20011e5..3ddd961da09 100644
--- a/reportbuilder/classes/local/aggregation/countdistinct.php
+++ b/reportbuilder/classes/local/aggregation/countdistinct.php
@@ -86,9 +86,10 @@ class countdistinct extends base {
      * @param mixed $value
      * @param array $values
      * @param array $callbacks
-     * @return mixed
+     * @param int $columntype
+     * @return int
      */
-    public static function format_value($value, array $values, array $callbacks) {
+    public static function format_value($value, array $values, array $callbacks, int $columntype): int {
         return (int) reset($values);
     }
 }
diff --git a/reportbuilder/classes/local/aggregation/groupconcat.php b/reportbuilder/classes/local/aggregation/groupconcat.php
index 9d7daec241e..e3572a9eba7 100644
--- a/reportbuilder/classes/local/aggregation/groupconcat.php
+++ b/reportbuilder/classes/local/aggregation/groupconcat.php
@@ -104,9 +104,10 @@ class groupconcat extends base {
      * @param mixed $value
      * @param array $values
      * @param array $callbacks
+     * @param int $columntype
      * @return mixed
      */
-    public static function format_value($value, array $values, array $callbacks) {
+    public static function format_value($value, array $values, array $callbacks, int $columntype) {
         $formattedvalues = [];
 
         // Store original names of all values that would be present without aggregation.
@@ -123,11 +124,11 @@ class groupconcat extends base {
                 continue;
             }
 
-            $originalvalue = array_combine($valuenames, $valuedata);
-            $originalfirstvalue = reset($originalvalue);
+            $originalvalues = array_combine($valuenames, $valuedata);
+            $originalvalue = column::get_default_value($originalvalues, $columntype);
 
             // Once we've re-constructed each value, we can apply callbacks to it.
-            $formattedvalues[] = parent::format_value($originalfirstvalue, $originalvalue, $callbacks);
+            $formattedvalues[] = parent::format_value($originalvalue, $originalvalues, $callbacks, $columntype);
         }
 
         return implode(', ', $formattedvalues);
diff --git a/reportbuilder/classes/local/aggregation/percent.php b/reportbuilder/classes/local/aggregation/percent.php
index 29b9878196c..de10bfa00d0 100644
--- a/reportbuilder/classes/local/aggregation/percent.php
+++ b/reportbuilder/classes/local/aggregation/percent.php
@@ -69,9 +69,10 @@ class percent extends base {
      * @param mixed $value
      * @param array $values
      * @param array $callbacks
-     * @return mixed
+     * @param int $columntype
+     * @return string
      */
-    public static function format_value($value, array $values, array $callbacks) {
-        return format::percent(reset($values));
+    public static function format_value($value, array $values, array $callbacks, int $columntype): string {
+        return format::percent((float) reset($values));
     }
 }
diff --git a/reportbuilder/classes/local/aggregation/sum.php b/reportbuilder/classes/local/aggregation/sum.php
index 119fb52f508..54a27754136 100644
--- a/reportbuilder/classes/local/aggregation/sum.php
+++ b/reportbuilder/classes/local/aggregation/sum.php
@@ -70,9 +70,10 @@ class sum extends base {
      * @param mixed $value
      * @param array $values
      * @param array $callbacks
-     * @return mixed
+     * @param int $columntype
+     * @return int
      */
-    public static function format_value($value, array $values, array $callbacks) {
+    public static function format_value($value, array $values, array $callbacks, int $columntype): int {
         return (int) reset($values);
     }
 }
diff --git a/reportbuilder/classes/local/helpers/format.php b/reportbuilder/classes/local/helpers/format.php
index 0ac617e6e40..a727bed428f 100644
--- a/reportbuilder/classes/local/helpers/format.php
+++ b/reportbuilder/classes/local/helpers/format.php
@@ -23,9 +23,6 @@ use stdClass;
 /**
  * Class containing helper methods for formatting column data via callbacks
  *
- * Note that type hints for each $value argument are avoided to allow for these callbacks to be executed when columns are
- * aggregated using one of the "Group concatenation" methods, where the value is typically stringified
- *
  * @package     core_reportbuilder
  * @copyright   2021 Sara Arjona <sara@moodle.com> based on Alberto Lara Hernández <albertolara@moodle.com> code.
  * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
@@ -40,8 +37,8 @@ class format {
      * @param string|null $format Format string for strftime
      * @return string
      */
-    public static function userdate($value, stdClass $row, ?string $format = null): string {
-        return $value ? userdate((int) $value, $format) : '';
+    public static function userdate(int $value, stdClass $row, ?string $format = null): string {
+        return $value ? userdate($value, $format) : '';
     }
 
     /**
@@ -50,8 +47,8 @@ class format {
      * @param bool $value
      * @return string
      */
-    public static function boolean_as_text($value): string {
-        return (bool) $value ? get_string('yes') : get_string('no');
+    public static function boolean_as_text(bool $value): string {
+        return $value ? get_string('yes') : get_string('no');
     }
 
     /**
@@ -60,7 +57,7 @@ class format {
      * @param float $value
      * @return string
      */
-    public static function percent($value): string {
-        return format_float((float) $value, 1) . '%';
+    public static function percent(float $value): string {
+        return format_float($value, 1) . '%';
     }
 }
diff --git a/reportbuilder/classes/local/report/column.php b/reportbuilder/classes/local/report/column.php
index d0177c3e4e6..fc174af00af 100644
--- a/reportbuilder/classes/local/report/column.php
+++ b/reportbuilder/classes/local/report/column.php
@@ -645,13 +645,14 @@ final class column {
      * Return the default column value, that being the value of it's first field
      *
      * @param array $values
+     * @param int $columntype
      * @return mixed
      */
-    private function get_default_value(array $values) {
+    public static function get_default_value(array $values, int $columntype) {
         $value = reset($values);
 
         // Ensure default value is cast to it's strict type.
-        switch ($this->get_type()) {
+        switch ($columntype) {
             case self::TYPE_INTEGER:
             case self::TYPE_TIMESTAMP:
                 $value = (int) $value;
@@ -675,11 +676,11 @@ final class column {
      */
     public function format_value(array $row) {
         $values = $this->get_values($row);
-        $value = $this->get_default_value($values);
+        $value = self::get_default_value($values, $this->type);
 
         // If column is being aggregated then defer formatting to them, otherwise loop through all column callbacks.
         if (!empty($this->aggregation)) {
-            $value = $this->aggregation::format_value($value, $values, $this->callbacks);
+            $value = $this->aggregation::format_value($value, $values, $this->callbacks, $this->type);
         } else {
             foreach ($this->callbacks as $callback) {
                 [$callable, $arguments] = $callback;
diff --git a/reportbuilder/tests/local/report/column_test.php b/reportbuilder/tests/local/report/column_test.php
index 4442747fd54..721b1a7b3b8 100644
--- a/reportbuilder/tests/local/report/column_test.php
+++ b/reportbuilder/tests/local/report/column_test.php
@@ -311,11 +311,11 @@ class column_test extends advanced_testcase {
     }
 
     /**
-     * Data provider for {@see test_format_value}
+     * Data provider for {@see test_get_default_value} and {@see test_format_value}
      *
      * @return array[]
      */
-    public function format_value_provider(): array {
+    public function column_type_provider(): array {
         return [
             [column::TYPE_INTEGER, 42],
             [column::TYPE_TEXT, 'Hello'],
@@ -327,13 +327,31 @@ class column_test extends advanced_testcase {
     }
 
     /**
-     * Test that column value is returned as correctly (value plus type)
+     * Test default value is returned from selected values, with correct type
      *
      * @param int $columntype
      * @param mixed $value
      * @param mixed|null $expected Expected value, or null to indicate it should be identical to value
      *
-     * @dataProvider format_value_provider
+     * @dataProvider column_type_provider
+     */
+    public function test_get_default_value(int $columntype, $value, $expected = null): void {
+        $defaultvalue = column::get_default_value([
+            'value' => $value,
+            'foo' => 'bar',
+        ], $columntype);
+
+        $this->assertSame($expected ?? $value, $defaultvalue);
+    }
+
+    /**
+     * Test that column value is returned correctly, with correct type
+     *
+     * @param int $columntype
+     * @param mixed $value
+     * @param mixed|null $expected Expected value, or null to indicate it should be identical to value
+     *
+     * @dataProvider column_type_provider
      */
     public function test_format_value(int $columntype, $value, $expected = null): void {
         $column = $this->create_column('test')
diff --git a/reportbuilder/upgrade.txt b/reportbuilder/upgrade.txt
index 098f51098a0..6f350d353a6 100644
--- a/reportbuilder/upgrade.txt
+++ b/reportbuilder/upgrade.txt
@@ -3,9 +3,10 @@ Information provided here is intended especially for developers.
 
 === 4.1 ===
 * 'set_default_per_page' and 'get_default_per_page' methods have been added to \local\report\base class
-   to manage the default displayed rows per page.
+  to manage the default displayed rows per page.
 * Added two new methods in the datasource class:
     - add_all_from_entity() to add all columns/filters/conditions from the given entity to the report at once
     - add_all_from_entities() to add all columns/filters/conditions from all the entities added to the report at once
-=======
 * New database helper methods for generating multiple unique values: `generate_aliases` and `generate_param_names`
+* The base aggregation `format_value` method has a `$columntype` argument in order to preserve type during aggregation. When
+  defining column callbacks, strict typing will now be preserved in your callback methods when the column is being aggregated