diff --git a/wp-includes/wp-db.php b/wp-includes/wp-db.php
index d37e51370e..fefbe8a284 100644
--- a/wp-includes/wp-db.php
+++ b/wp-includes/wp-db.php
@@ -570,19 +570,12 @@ class wpdb {
 		if ( WP_DEBUG && WP_DEBUG_DISPLAY )
 			$this->show_errors();
 
-		/* Use ext/mysqli if it exists and:
-		 *  - WP_USE_EXT_MYSQL is defined as false, or
-		 *  - We are a development version of WordPress, or
-		 *  - We are running PHP 5.5 or greater, or
-		 *  - ext/mysql is not loaded.
-		 */
+		// Use ext/mysqli if it exists unless WP_USE_EXT_MYSQL is defined as true
 		if ( function_exists( 'mysqli_connect' ) ) {
+			$this->use_mysqli = true;
+
 			if ( defined( 'WP_USE_EXT_MYSQL' ) ) {
 				$this->use_mysqli = ! WP_USE_EXT_MYSQL;
-			} elseif ( version_compare( phpversion(), '5.5', '>=' ) || ! function_exists( 'mysql_connect' ) ) {
-				$this->use_mysqli = true;
-			} elseif ( false !== strpos( $GLOBALS['wp_version'], '-' ) ) {
-				$this->use_mysqli = true;
 			}
 		}