diff --git a/R/course.R b/R/course.R
index 7ba4f0c02..ce2389576 100644
--- a/R/course.R
+++ b/R/course.R
@@ -529,7 +529,7 @@ top_directory <- function(filenames) {
   in_top <- path_dir(filenames) == "."
   unique_top <- unique(filenames[in_top])
   is_directory <- grepl("/$", unique_top)
-  if(length(unique(path_dir(filenames)))==1 & length(unique_top) == 0){
+  if (length(unique(path_dir(filenames))) == 1 && length(unique_top) == 0) {
     unique_top <- unique(path_dir(filenames))
   } else {
     if (length(unique_top) > 1 || !is_directory) {