diff --git a/phpBB/language/en/posting.php b/phpBB/language/en/posting.php
index 570cf63f17..426475e77a 100644
--- a/phpBB/language/en/posting.php
+++ b/phpBB/language/en/posting.php
@@ -140,7 +140,6 @@ $lang = array_merge($lang, array(
 	'IMAGES_ARE_OFF'			=> '[img] is <em>OFF</em>',
 	'IMAGES_ARE_ON'				=> '[img] is <em>ON</em>',
 	'INVALID_FILENAME'			=> '%s is an invalid filename.',
-	'INVALID_FONT_SIZE'			=> 'The font size you supplied is invalid: %s',
 
 	'LOAD'						=> 'Load',
 	'LOAD_DRAFT'				=> 'Load draft',
diff --git a/phpBB/phpbb/textformatter/s9e/parser.php b/phpBB/phpbb/textformatter/s9e/parser.php
index 1bc56a8cb4..a36fc63141 100644
--- a/phpBB/phpbb/textformatter/s9e/parser.php
+++ b/phpBB/phpbb/textformatter/s9e/parser.php
@@ -228,10 +228,6 @@ class parser implements \phpbb\textformatter\parser_interface
 			{
 				$errors[] = array($msg);
 			}
-			else if ($msg === 'INVALID_FONT_SIZE')
-			{
-				$errors[] = [$msg, $context['invalid_size']];
-			}
 		}
 
 		// Deduplicate error messages. array_unique() only works on strings so we have to serialize
@@ -339,13 +335,6 @@ class parser implements \phpbb\textformatter\parser_interface
 	*/
 	static public function filter_font_size($size, $max_size, Logger $logger)
 	{
-		if (!is_numeric($size))
-		{
-			$logger->err('INVALID_FONT_SIZE', ['invalid_size' => htmlspecialchars($size)]);
-
-			return false;
-		}
-
 		if ($max_size && $size > $max_size)
 		{
 			$logger->err('MAX_FONT_SIZE_EXCEEDED', array('max_size' => $max_size));
@@ -353,7 +342,7 @@ class parser implements \phpbb\textformatter\parser_interface
 			return false;
 		}
 
-		if ($size < 1)
+		if ($size < 1 || !is_numeric($size))
 		{
 			return false;
 		}