diff --git a/chain/store/index.go b/chain/store/index.go
index 8747c79c6..bb363ec18 100644
--- a/chain/store/index.go
+++ b/chain/store/index.go
@@ -91,16 +91,11 @@ func (ci *ChainIndex) fillCache(tsk types.TipSetKey) (*lbEntry, error) {
 		return nil, err
 	}
 
-	if parent.Height() > rheight {
-		return nil, xerrors.Errorf("cache is inconsistent")
-	}
-
 	rheight -= ci.skipLength
 
 	var skipTarget *types.TipSet
 	if parent.Height() < rheight {
 		skipTarget = parent
-
 	} else {
 		skipTarget, err = ci.walkBack(parent, rheight)
 		if err != nil {
@@ -119,8 +114,9 @@ func (ci *ChainIndex) fillCache(tsk types.TipSetKey) (*lbEntry, error) {
 	return lbe, nil
 }
 
+// floors to nearest skipLength multiple
 func (ci *ChainIndex) roundHeight(h abi.ChainEpoch) abi.ChainEpoch {
-	return abi.ChainEpoch(h/ci.skipLength) * ci.skipLength
+	return (h / ci.skipLength) * ci.skipLength
 }
 
 func (ci *ChainIndex) roundDown(ts *types.TipSet) (*types.TipSet, error) {
@@ -152,6 +148,8 @@ func (ci *ChainIndex) walkBack(from *types.TipSet, to abi.ChainEpoch) (*types.Ti
 		}
 
 		if to > pts.Height() {
+			// in case pts is lower than the epoch we're looking for (null blocks)
+			// return a tipset above that height
 			return ts, nil
 		}
 		if to == pts.Height() {
diff --git a/chain/store/index_test.go b/chain/store/index_test.go
index b1a85996f..73f4901f0 100644
--- a/chain/store/index_test.go
+++ b/chain/store/index_test.go
@@ -44,7 +44,8 @@ func TestIndexSeeks(t *testing.T) {
 	}
 	cs.SetGenesis(gen)
 
-	for i := 0; i < 100; i++ {
+	// Put 113 blocks from genesis
+	for i := 0; i < 113; i++ {
 		nextts := mock.TipSet(mock.MkBlock(cur, 1, 1))
 
 		if err := cs.PutTipSet(ctx, nextts); err != nil {
@@ -53,6 +54,7 @@ func TestIndexSeeks(t *testing.T) {
 		cur = nextts
 	}
 
+	// Put 50 null epochs + 1 block
 	skip := mock.MkBlock(cur, 1, 1)
 	skip.Height += 50
 
@@ -66,9 +68,9 @@ func TestIndexSeeks(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	assert.Equal(t, abi.ChainEpoch(151), ts.Height())
+	assert.Equal(t, abi.ChainEpoch(164), ts.Height())
 
-	for i := 0; i <= 100; i++ {
+	for i := 0; i <= 113; i++ {
 		ts3, err := cs.GetTipsetByHeight(ctx, abi.ChainEpoch(i), skipts, false)
 		if err != nil {
 			t.Fatal(err)