diff --git a/cmd/lotus-shed/main.go b/cmd/lotus-shed/main.go
index 1f4d953f9..9cb1cd32c 100644
--- a/cmd/lotus-shed/main.go
+++ b/cmd/lotus-shed/main.go
@@ -86,6 +86,7 @@ func main() {
 		replayOfflineCmd,
 		msgindexCmd,
 		FevmAnalyticsCmd,
+		mismatchesCmd,
 	}
 
 	app := &cli.App{
diff --git a/cmd/lotus-shed/mismatches.go b/cmd/lotus-shed/mismatches.go
new file mode 100644
index 000000000..223158e0f
--- /dev/null
+++ b/cmd/lotus-shed/mismatches.go
@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/urfave/cli/v2"
+
+	lcli "github.com/filecoin-project/lotus/cli"
+)
+
+var mismatchesCmd = &cli.Command{
+	Name:        "mismatches",
+	Description: "Walk up the chain, recomputing state, and reporting any mismatches",
+	Action: func(cctx *cli.Context) error {
+		srv, err := lcli.GetFullNodeServices(cctx)
+		if err != nil {
+			return err
+		}
+		defer srv.Close() //nolint:errcheck
+
+		api := srv.FullNodeAPI()
+		ctx := lcli.ReqContext(cctx)
+
+		checkTs, err := api.ChainHead(ctx)
+		if err != nil {
+			return err
+		}
+
+		for checkTs.Height() != 0 {
+			if checkTs.Height()%10000 == 0 {
+				fmt.Println("Reached height ", checkTs.Height())
+			}
+
+			execTsk := checkTs.Parents()
+			execTs, err := api.ChainGetTipSet(ctx, execTsk)
+			if err != nil {
+				return err
+			}
+
+			st, err := api.StateCompute(ctx, execTs.Height(), nil, execTsk)
+			if err != nil {
+				return err
+			}
+
+			if st.Root != checkTs.ParentState() {
+				fmt.Println("consensus mismatch found at height ", execTs.Height())
+			}
+
+			checkTs = execTs
+		}
+
+		return nil
+	},
+}
diff --git a/extern/filecoin-ffi b/extern/filecoin-ffi
index 86698251a..de34caff9 160000
--- a/extern/filecoin-ffi
+++ b/extern/filecoin-ffi
@@ -1 +1 @@
-Subproject commit 86698251ab87eec6944320a01998623155c01276
+Subproject commit de34caff946d598edb299566d951b44b9b7f7dd4