diff --git a/wp-admin/admin-functions.php b/wp-admin/admin-functions.php
index c6dcc56052..fdfeb38019 100644
--- a/wp-admin/admin-functions.php
+++ b/wp-admin/admin-functions.php
@@ -1877,6 +1877,7 @@ function wp_handle_upload(&$file, $overrides = false) {
 			else
 				$filename = str_replace("$number$ext", ++$number . $ext, $filename);
 		}
+		$filename = preg_replace('#\.(?![^.]+$)#', '-', $filename);
 	}
 
 	// Move the file to the uploads dir