diff --git a/src/boot/driver/lib.ml b/src/boot/driver/lib.ml
index 764fd68848f..71b310b0bc2 100644
--- a/src/boot/driver/lib.ml
+++ b/src/boot/driver/lib.ml
@@ -176,7 +176,8 @@ let get_mod
           let dh = Unix.opendir dir in
           let rec scan _ =
             try
-              let file = Unix.readdir dh in
+              let basename = Unix.readdir dh in
+              let file = dir ^ "/" ^ basename in
                 log sess "considering file %s" file;
                 if (Filename.check_suffix file suffix) &&
                   (file_matches file)