diff --git a/lib/cache.ml b/lib/cache.ml
index 19607e0..db70a0a 100644
--- a/lib/cache.ml
+++ b/lib/cache.ml
@@ -24,7 +24,17 @@ let current c out = Hashtbl.find_opt c.keys out
 let put c out key = Hashtbl.replace c.keys out key
 let drop c out = Hashtbl.remove c.keys out
 
-let digest_file p = match Digest.file p with d -> Some (Digest.to_hex d) | exception Sys_error _ -> None
+let digests : (string, string option) Hashtbl.t = Hashtbl.create 256
+
+let digest_file p =
+  match Hashtbl.find_opt digests p with
+  | Some d -> d
+  | None ->
+      let d = match Digest.file p with d -> Some (Digest.to_hex d) | exception Sys_error _ -> None in
+      Hashtbl.replace digests p d;
+      d
+
+let forget p = Hashtbl.remove digests p
 
 let key ~cmd ~inputs =
   let b = Buffer.create 256 in
diff --git a/lib/sched.ml b/lib/sched.ml
index e7b184e..16e995b 100644
--- a/lib/sched.ml
+++ b/lib/sched.ml
@@ -78,11 +78,14 @@ let run g ~selected ~jobs ~cache ~verbose ~keep_going ~on_start ~on_done =
         if ok then begin
           incr built;
           state.(v.id) <- Done;
+          List.iter Cache.forget v.outs;
+          (match v.depfile with Some d -> Cache.forget d | None -> ());
           Cache.put cache (List.hd v.outs) (key_of v);
           release v.id
         end
         else begin
           incr failed;
+          List.iter Cache.forget v.outs;
           Cache.drop cache (List.hd v.outs);
           List.iter (fun o -> try Sys.remove o with Sys_error _ -> ()) v.outs;
           skip v.id