diff --git a/Sources/Db/APIs/MySQL.php b/Sources/Db/APIs/MySQL.php
index a8c0854d1a..3a1be9f16d 100644
--- a/Sources/Db/APIs/MySQL.php
+++ b/Sources/Db/APIs/MySQL.php
@@ -88,6 +88,11 @@ class MySQL extends DatabaseApi implements DatabaseApiInterface
 	 */
 	public bool $regex_tcl = true;
 
+	/**
+	 *
+	 */
+	public bool $regex_posix = true;
+
 	/*********************
 	 * Internal properties
 	 *********************/
@@ -2620,12 +2625,8 @@ protected function initialize(array $options = []): void
 
 		if ($this->get_vendor() === 'MariaDB') {
 			$this->regex_pcre = version_compare(preg_replace('/^(\d+(?:\.\d+)+).*/', '$1', $this->get_version()), '10.0.5', '>=');
-
-			$this->regex_tcl = !$this->regex_pcre;
 		} else {
 			$this->regex_icu = version_compare(preg_replace('/^(\d+(?:\.\d+)+).*/', '$1', $this->get_version()), '8.0.4', '>=');
-
-			$this->regex_tcl = !$this->regex_icu;
 		}
 
 		$this->character_set = strtolower($this->detect_charset('messages', 'body'));
diff --git a/Sources/Db/APIs/PostgreSQL.php b/Sources/Db/APIs/PostgreSQL.php
index 472242e4f6..54170f4f51 100644
--- a/Sources/Db/APIs/PostgreSQL.php
+++ b/Sources/Db/APIs/PostgreSQL.php
@@ -75,6 +75,11 @@ class PostgreSQL extends DatabaseApi implements DatabaseApiInterface
 	 */
 	public bool $regex_tcl = true;
 
+	/**
+	 *
+	 */
+	public bool $regex_posix = true;
+
 	/*********************
 	 * Internal properties
 	 *********************/
diff --git a/Sources/Db/DatabaseApi.php b/Sources/Db/DatabaseApi.php
index a2e0efddb0..d51f8e1edd 100644
--- a/Sources/Db/DatabaseApi.php
+++ b/Sources/Db/DatabaseApi.php
@@ -111,6 +111,13 @@ abstract class DatabaseApi
 	 */
 	public bool $regex_tcl;
 
+	/**
+	 * @var bool
+	 *
+	 * Whether the database supports POSIX regular expressions.
+	 */
+	public bool $regex_posix;
+
 	/**
 	 * @var string
 	 *
diff --git a/Sources/Search/SearchApi.php b/Sources/Search/SearchApi.php
index 53559dd214..5b9d3a9a37 100644
--- a/Sources/Search/SearchApi.php
+++ b/Sources/Search/SearchApi.php
@@ -1306,6 +1306,11 @@ protected function wordBoundaryWrapper(string $str): string
 			return \sprintf('\\y%s\\y', $str);
 		}
 
+		// POSIX uses `[[:<:]]` and `[[:>:]]` as the word boundaries.
+		if (Db::$db->regex_posix) {
+			return \sprintf('[[:<:]]%s[[:>:]]', $str);
+		}
+
 		// We should never get here, but just in case...
 		return $str;
 	}