diff --git a/application/ui.extkeywidget.class.inc.php b/application/ui.extkeywidget.class.inc.php
index 671d14847..4cec8e222 100644
--- a/application/ui.extkeywidget.class.inc.php
+++ b/application/ui.extkeywidget.class.inc.php
@@ -251,7 +251,7 @@ class UIExtKeyWidget
 						$aOption['picture_url'] = $oImage->GetDisplayURL($sClassAllowed, $oObj->GetKey(), $sObjectImageAttCode);
 						$aOption['initials'] = '';
 					} else {
-						$aOption['initials'] = utils::ToAcronym($oObj->Get('friendlyname'));
+						$aOption['initials'] = utils::FormatInitialsForMedallion(utils::ToAcronym($oObj->Get('friendlyname')));
 					}
 				}
 				array_push($aOptions, $aOption);
@@ -829,7 +829,7 @@ JS
 					}
 
 					if (array_key_exists('initials', $aValue)) {
-						$aElt['initials'] = $aValue['initials'];
+						$aElt['initials'] = utils::FormatInitialsForMedallion($aValue['initials']);
 						if (array_key_exists('picture_url', $aValue)) {
 							$aElt['picture_url'] = $aValue['picture_url'];
 						}
diff --git a/application/utils.inc.php b/application/utils.inc.php
index 98a09758f..469c9dd22 100644
--- a/application/utils.inc.php
+++ b/application/utils.inc.php
@@ -3050,6 +3050,20 @@ HTML;
 		return $aMentionedObjects;
 	}
 
+	/**
+	 * Note: This method is not ideal, but other solutions seemed even less ideal:
+	 *   * Add a "$sMaxLength" param. to utils::ToAcronym(): Does not work for every use cases (see corresponding ticket) as in some parts utils::ToAcronym isn't necessarly meant to be used in a medallion.
+	 *
+	 * @param string $sInitials
+	 *
+	 * @return string Truncates $sInitials so it can fit in medallions
+	 * @since 3.0.1 N°4913
+	 */
+	public static function FormatInitialsForMedallion(string $sInitials): string
+	{
+		return mb_substr($sInitials, 0, 3);
+	}
+
 	/**
 	 * @param $sUrl
 	 * @param string $sParamName
diff --git a/pages/ajax.render.php b/pages/ajax.render.php
index d029f79b7..db3e34c24 100644
--- a/pages/ajax.render.php
+++ b/pages/ajax.render.php
@@ -2539,7 +2539,7 @@ EOF
 						} else {
 							// If no image found, fallback on initials
 							$aMatch['picture_style'] = '';
-							$aMatch['initials'] = utils::ToAcronym($oObject->Get('friendlyname'));
+							$aMatch['initials'] = utils::FormatInitialsForMedallion(utils::ToAcronym($oObject->Get('friendlyname')));
 						}
 					}
 
diff --git a/sources/Renderer/Bootstrap/FieldRenderer/BsSimpleFieldRenderer.php b/sources/Renderer/Bootstrap/FieldRenderer/BsSimpleFieldRenderer.php
index 495223db5..aedd0918c 100644
--- a/sources/Renderer/Bootstrap/FieldRenderer/BsSimpleFieldRenderer.php
+++ b/sources/Renderer/Bootstrap/FieldRenderer/BsSimpleFieldRenderer.php
@@ -648,7 +648,7 @@ HTML
 					// Open medallion from profile picture or first name letter
 					$bEntryHasMedallionPicture = (empty($aContactPicturesCache[$iEntryUserId]) === false);
 					$sEntryMedallionStyle = $bEntryHasMedallionPicture ? ' background-image: url(\''.$aContactPicturesCache[$iEntryUserId].'\');' : '';
-					$sEntryMedallionContent = $bEntryHasMedallionPicture ? '' : UserRights::GetUserInitials($sEntryUserLogin);
+					$sEntryMedallionContent = $bEntryHasMedallionPicture ? '' : utils::FormatInitialsForMedallion(UserRights::GetUserInitials($sEntryUserLogin));
 					// - Entry tooltip
 					$sEntryMedallionTooltip = utils::HtmlEntities($sEntryUserLogin);
 					$sEntryMedallionTooltipPlacement = ($iEntryUserId === $iCurrentUserId) ? 'left' : 'right';
diff --git a/templates/base/layouts/activity-panel/activity-entry/layout.html.twig b/templates/base/layouts/activity-panel/activity-entry/layout.html.twig
index bae577579..d7fa10811 100644
--- a/templates/base/layouts/activity-panel/activity-entry/layout.html.twig
+++ b/templates/base/layouts/activity-panel/activity-entry/layout.html.twig
@@ -10,7 +10,7 @@
 			{% if oUIBlock.GetAuthorPictureAbsUrl() is not empty %}
 				<img class="ibo-activity-entry--author-picture" src="{{ oUIBlock.GetAuthorPictureAbsUrl() }}" alt="{{ oUIBlock.GetAuthorInitials() }}">
 			{% else %}
-				<div class="ibo-activity-entry--author-initials">{{ oUIBlock.GetAuthorInitials() }}</div>
+				<div class="ibo-activity-entry--author-initials">{{ oUIBlock.GetAuthorInitials()|slice(0, 3) }}</div>
 			{% endif %}
 		{% endblock %}
 	</div>
diff --git a/test/application/UtilsTest.php b/test/application/UtilsTest.php
index 9be069475..1b425ccda 100644
--- a/test/application/UtilsTest.php
+++ b/test/application/UtilsTest.php
@@ -554,6 +554,40 @@ class UtilsTest extends \Combodo\iTop\Test\UnitTest\ItopTestCase
 		];
 	}
 
+	/**
+	 * @dataProvider FormatInitialsForMedallionProvider
+	 * @covers utils::FormatInitialsForMedallion
+	 *
+	 * @param string $sInput
+	 * @param string $sExpected
+	 */
+	public function testFormatInitialsForMedallion(string $sInput, string $sExpected)
+	{
+		$sTested = utils::FormatInitialsForMedallion($sInput);
+		$this->assertEquals($sExpected, $sTested);
+	}
+
+	/**
+	 * @since 3.0.1
+	 */
+	public function FormatInitialsForMedallionProvider()
+	{
+		return [
+			'All letters kept (2)' => [
+				'AB',
+				'AB',
+			],
+			'All letters kept (3)' => [
+				'ABC',
+				'ABC',
+			],
+			'Only 3 first letters kept (4)' => [
+				'ABCD',
+				'ABC',
+			],
+		];
+	}
+
 	/**
 	 * @param string $sExpressionToConvert
 	 * @param int $iExpectedConvertedValue