diff --git a/administrator/components/com_jedchecker/language/en-GB/en-GB.com_jedchecker.ini b/administrator/components/com_jedchecker/language/en-GB/en-GB.com_jedchecker.ini
index dba071f..25337b3 100644
--- a/administrator/components/com_jedchecker/language/en-GB/en-GB.com_jedchecker.ini
+++ b/administrator/components/com_jedchecker/language/en-GB/en-GB.com_jedchecker.ini
@@ -92,6 +92,7 @@ COM_JEDCHECKER_LANG_KEY_NOT_ASCII="The key name is not ASCII-compatible"
 COM_JEDCHECKER_LANG_KEY_NOT_UPPERCASE="The key name is not uppercase"
 COM_JEDCHECKER_LANG_KEY_DUPLICATED="The key name was declared previously on line %d"
 COM_JEDCHECKER_LANG_TRANSLATION_ERROR="Invalid translation string"
+COM_JEDCHECKER_LANG_INVALID_UTF8="Invalid UTF8 string"
 COM_JEDCHECKER_LANG_TRANSLATION_QUOTES="All translation strings should be enclosed in double quotation marks"
 COM_JEDCHECKER_LANG_TRANSLATION_EMPTY="Empty translation string"
 COM_JEDCHECKER_LANG_QQ_DEPRECATED="Usage of \"_QQ_\" is deprecated since Joomla! 3.9. Use escaped double quotes (\\\") instead"
diff --git a/administrator/components/com_jedchecker/libraries/rules/language.php b/administrator/components/com_jedchecker/libraries/rules/language.php
index fe9ac4b..b883617 100644
--- a/administrator/components/com_jedchecker/libraries/rules/language.php
+++ b/administrator/components/com_jedchecker/libraries/rules/language.php
@@ -96,6 +96,9 @@ class JedcheckerRulesLanguage extends JEDcheckerRule
 		$nLines = count($lines);
 		$keys = array();
 
+		// Use mb_check_encoding (if exists) to validate UTF-8
+		$mbExists = function_exists('mb_check_encoding');
+
 		for ($lineno = 0; $lineno < $nLines; $lineno++)
 		{
 			$startLineno = $lineno + 1;
@@ -223,6 +226,14 @@ class JedcheckerRulesLanguage extends JEDcheckerRule
 				continue;
 			}
 
+			// Check it's a valid UTF-8 string
+			$validUTF8 = $mbExists ? mb_check_encoding($value, 'UTF-8') : preg_match('//u', $value);
+
+			if (!$validUTF8)
+			{
+				$this->report->addWarning($file, JText::_('COM_JEDCHECKER_LANG_INVALID_UTF8'), $startLineno, $line);
+			}
+
 			if (strlen($value) < 2 || $value[0] !== '"' || substr($value, -1) !== '"')
 			{
 				$this->report->addError($file, JText::_('COM_JEDCHECKER_LANG_TRANSLATION_QUOTES'), $startLineno, $line);