diff --git a/rpc/args.go b/rpc/args.go
index b23216c98..206472aa2 100644
--- a/rpc/args.go
+++ b/rpc/args.go
@@ -424,17 +424,20 @@ func (args *BlockFilterArgs) UnmarshalJSON(b []byte) (err error) {
 		return NewInsufficientParamsError(len(obj), 1)
 	}
 
-	fromstr, ok := obj[0].FromBlock.(string)
-	if !ok {
-		return NewInvalidTypeError("fromBlock", "is not a string")
+	var num int64
+	if err := blockHeight(obj[0].FromBlock, &num); err != nil {
+		return err
+	}
+	if num < 0 {
+		args.Earliest = -1 //latest block
+	} else {
+		args.Earliest = num
 	}
 
-	switch fromstr {
-	case "latest":
-		args.Earliest = -1
-	default:
-		args.Earliest = int64(common.Big(obj[0].FromBlock.(string)).Int64())
+	if err := blockHeight(obj[0].ToBlock, &num); err != nil {
+		return err
 	}
+	args.Latest = num
 
 	tostr, ok := obj[0].ToBlock.(string)
 	if !ok {
diff --git a/rpc/args_test.go b/rpc/args_test.go
index 0c7360c53..2622891b9 100644
--- a/rpc/args_test.go
+++ b/rpc/args_test.go
@@ -759,10 +759,10 @@ func TestBlockFilterArgsWords(t *testing.T) {
 	}
 }
 
-func TestBlockFilterArgsNums(t *testing.T) {
+func TestBlockFilterArgsBool(t *testing.T) {
 	input := `[{
-  "fromBlock": 2,
-  "toBlock": 3
+  "fromBlock": true,
+  "toBlock": false
   }]`
 
 	args := new(BlockFilterArgs)