2 files changed, 2 insertions, 1 deletions
diff --git a/Changes b/Changes
index 08d87907c..de3aeeb83 100644
--- a/Changes
+++ b/Changes
@@ -39,6 +39,7 @@ OCaml 4.00.2:
 -------------
 
 Bug fixes:
+- PR#5102: ocamlbuild fails when using an unbound variable in rule dependency
 - PR#5240: register exception printers for Unix.Unix_error and Dynlink.Error
 - PR#5300: verbose parameter should implicitly set classic display
 - PR#5772: problem with marshaling of mutually-recursive functions
diff --git a/ocamlbuild/resource.ml b/ocamlbuild/resource.ml
index 2ef42487e..4121d194a 100644
--- a/ocamlbuild/resource.ml
+++ b/ocamlbuild/resource.ml
@@ -377,7 +377,7 @@ end = struct
       List.map begin fun x ->
         match x with
         | A atom -> atom
-        | V(var, _) -> List.assoc var env
+        | V(var, _) -> try List.assoc var env with Not_found -> (* unbound variable *) ""
       end s
     end
 end