diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index d726c07313..e0e98be7a5 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -1575,10 +1575,12 @@ function path_join( $base, $path ) {
 /**
  * Normalize a filesystem path.
  *
- * Replaces backslashes with forward slashes for Windows systems, and ensures
- * no duplicate slashes exist.
+ * On windows systems, replaces backslashes with forward slashes
+ * and forces upper-case drive letters.
+ * Ensures that no duplicate slashes exist.
  *
  * @since 3.9.0
+ * @since 4.4.0 Ensures upper-case drive letters on Windows systems.
  *
  * @param string $path Path to normalize.
  * @return string Normalized path.
@@ -1586,6 +1588,9 @@ function path_join( $base, $path ) {
 function wp_normalize_path( $path ) {
 	$path = str_replace( '\\', '/', $path );
 	$path = preg_replace( '|/+|','/', $path );
+	if ( ':' === substr( $path, 1, 1 ) ) {
+		$path = ucfirst( $path );
+	}
 	return $path;
 }
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index b8e3f8a574..c0618eb74b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-34103';
+$wp_version = '4.4-alpha-34104';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.