diff --git a/chain/gen/mining.go b/chain/gen/mining.go
index ad8dfdf5b..bc809a888 100644
--- a/chain/gen/mining.go
+++ b/chain/gen/mining.go
@@ -150,6 +150,17 @@ func aggregateSignatures(sigs []crypto.Signature) (*crypto.Signature, error) {
 	}
 
 	aggSig := bls.Aggregate(blsSigs)
+	if aggSig == nil {
+		if len(sigs) > 0 {
+			return nil, xerrors.Errorf("bls.Aggregate returned nil with %d signatures", len(sigs))
+		}
+
+		return &crypto.Signature{
+			Type: crypto.SigTypeBLS,
+			Data: new(bls.Signature)[:],
+		}, nil
+	}
+
 	return &crypto.Signature{
 		Type: crypto.SigTypeBLS,
 		Data: aggSig[:],
diff --git a/extern/filecoin-ffi b/extern/filecoin-ffi
index ca281af0b..5342c7c97 160000
--- a/extern/filecoin-ffi
+++ b/extern/filecoin-ffi
@@ -1 +1 @@
-Subproject commit ca281af0b6c00314382a75ae869e5cb22c83655b
+Subproject commit 5342c7c97d1a1df4650629d14f2823d52889edd9
diff --git a/go.mod b/go.mod
index 90b4f1f65..355bc160f 100644
--- a/go.mod
+++ b/go.mod
@@ -29,7 +29,7 @@ require (
 	github.com/filecoin-project/go-paramfetch v0.0.2-0.20200605171344-fcac609550ca
 	github.com/filecoin-project/go-statestore v0.1.0
 	github.com/filecoin-project/go-storedcounter v0.0.0-20200421200003-1c99c62e8a5b
-	github.com/filecoin-project/sector-storage v0.0.0-20200625154333-98ef8e4ef246
+	github.com/filecoin-project/sector-storage v0.0.0-20200630180318-4c1968f62a8f
 	github.com/filecoin-project/specs-actors v0.6.2-0.20200617175406-de392ca14121
 	github.com/filecoin-project/specs-storage v0.1.1-0.20200622113353-88a9704877ea
 	github.com/filecoin-project/storage-fsm v0.0.0-20200625160832-379a4655b044
diff --git a/go.sum b/go.sum
index 0ee5cc615..45316da02 100644
--- a/go.sum
+++ b/go.sum
@@ -256,9 +256,12 @@ github.com/filecoin-project/go-storedcounter v0.0.0-20200421200003-1c99c62e8a5b/
 github.com/filecoin-project/sector-storage v0.0.0-20200615154852-728a47ab99d6/go.mod h1:M59QnAeA/oV+Z8oHFLoNpGMv0LZ8Rll+vHVXX7GirPM=
 github.com/filecoin-project/sector-storage v0.0.0-20200625154333-98ef8e4ef246 h1:NfYQRmVRe0LzlNbK5Ket3vbBOwFD5TvtcNtfo/Sd8mg=
 github.com/filecoin-project/sector-storage v0.0.0-20200625154333-98ef8e4ef246/go.mod h1:8f0hWDzzIi1hKs4IVKH9RnDsO4LEHVz8BNat0okDOuY=
+github.com/filecoin-project/sector-storage v0.0.0-20200630180318-4c1968f62a8f h1:EHKqNJNIcYggqfrd5nu7SV1KR93ReZygfdSV0w/jefQ=
+github.com/filecoin-project/sector-storage v0.0.0-20200630180318-4c1968f62a8f/go.mod h1:r12d7tsmJKz8QDGoCvl65Ay2al6mOgDqxAGUxbyrgMs=
 github.com/filecoin-project/specs-actors v0.0.0-20200210130641-2d1fbd8672cf/go.mod h1:xtDZUB6pe4Pksa/bAJbJ693OilaC5Wbot9jMhLm3cZA=
 github.com/filecoin-project/specs-actors v0.3.0/go.mod h1:nQYnFbQ7Y0bHZyq6HDEuVlCPR+U3z5Q3wMOQ+2aiV+Y=
 github.com/filecoin-project/specs-actors v0.6.0/go.mod h1:dRdy3cURykh2R8O/DKqy8olScl70rmIS7GrB4hB1IDY=
+github.com/filecoin-project/specs-actors v0.6.1/go.mod h1:dRdy3cURykh2R8O/DKqy8olScl70rmIS7GrB4hB1IDY=
 github.com/filecoin-project/specs-actors v0.6.2-0.20200617175406-de392ca14121 h1:oRA+b4iN4H86xXDXbU3TOyvmBZp7//c5VqTc0oJ6nLg=
 github.com/filecoin-project/specs-actors v0.6.2-0.20200617175406-de392ca14121/go.mod h1:dRdy3cURykh2R8O/DKqy8olScl70rmIS7GrB4hB1IDY=
 github.com/filecoin-project/specs-storage v0.1.0 h1:PkDgTOT5W5Ao7752onjDl4QSv+sgOVdJbvFjOnD5w94=