diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 41428ce430..2cab41acd7 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -262,8 +262,15 @@ function is_serialized( $data, $strict = true ) {
 		if ( ';' !== $lastc && '}' !== $lastc )
 			return false;
 	} else {
-		// ensures ; or } exists but is not in the first X chars
-		if ( strpos( $data, ';' ) < 3 && strpos( $data, '}' ) < 4 )
+		$semicolon = strpos( $data, ';' );
+		$brace     = strpos( $data, '}' );
+		// Either ; or } must exist.
+		if ( false === $semicolon && false === $brace )
+			return false;
+		// But neither must be in the first X characters.
+		if ( false !== $semicolon && $semicolon < 3 )
+			return false;
+		if ( false !== $brace && $brace < 4 )
 			return false;
 	}
 	$token = $data[0];