diff --git a/common/math/big.go b/common/math/big.go
index 48427810e1..1c2afa749a 100644
--- a/common/math/big.go
+++ b/common/math/big.go
@@ -49,6 +49,17 @@ func NewHexOrDecimal256(x int64) *HexOrDecimal256 {
 	return &h
 }
 
+// UnmarshalJSON implements json.Unmarshaler.
+//
+// It is similar to UnmarshalText, but allows parsing real decimals too, not just
+// quoted decimal strings.
+func (i *HexOrDecimal256) UnmarshalJSON(input []byte) error {
+	if len(input) > 0 && input[0] == '"' {
+		input = input[1 : len(input)-1]
+	}
+	return i.UnmarshalText(input)
+}
+
 // UnmarshalText implements encoding.TextUnmarshaler.
 func (i *HexOrDecimal256) UnmarshalText(input []byte) error {
 	bigint, ok := ParseBig256(string(input))
diff --git a/common/math/integer.go b/common/math/integer.go
index 50d3eba1f5..da01c0a08e 100644
--- a/common/math/integer.go
+++ b/common/math/integer.go
@@ -41,6 +41,17 @@ const (
 // HexOrDecimal64 marshals uint64 as hex or decimal.
 type HexOrDecimal64 uint64
 
+// UnmarshalJSON implements json.Unmarshaler.
+//
+// It is similar to UnmarshalText, but allows parsing real decimals too, not just
+// quoted decimal strings.
+func (i *HexOrDecimal64) UnmarshalJSON(input []byte) error {
+	if len(input) > 0 && input[0] == '"' {
+		input = input[1 : len(input)-1]
+	}
+	return i.UnmarshalText(input)
+}
+
 // UnmarshalText implements encoding.TextUnmarshaler.
 func (i *HexOrDecimal64) UnmarshalText(input []byte) error {
 	int, ok := ParseUint64(string(input))