diff --git a/spec/Specification.md b/spec/Specification.md
index ab858e9b1..b2edd2a32 100644
--- a/spec/Specification.md
+++ b/spec/Specification.md
@@ -81,8 +81,8 @@ type Params struct {
 type BlockInfo struct {
 	// block height this transaction is executed
 	Height uint64 `json:"height"`
-	// time in nanoseconds since unix epoch. Uses string to ensure JavaScript compatibility.
-	Time    uint64 `json:"time,string"`
+	// time in nanoseconds since unix epoch. Uses Uint64 to ensure JavaScript compatibility.
+	Time    Uint64 `json:"time"`
 	ChainID string `json:"chain_id"`
 }
 
diff --git a/types/env.go b/types/env.go
index 9dc882b06..8ad0bbbe1 100644
--- a/types/env.go
+++ b/types/env.go
@@ -16,8 +16,8 @@ type Env struct {
 type BlockInfo struct {
 	// block height this transaction is executed
 	Height uint64 `json:"height"`
-	// time in nanoseconds since unix epoch. Uses string to ensure JavaScript compatibility.
-	Time    uint64 `json:"time,string"`
+	// time in nanoseconds since unix epoch. Uses Uint64 to ensure JavaScript compatibility.
+	Time    Uint64 `json:"time"`
 	ChainID string `json:"chain_id"`
 }
 
diff --git a/types/env_test.go b/types/env_test.go
index c460e345e..2cc092cab 100644
--- a/types/env_test.go
+++ b/types/env_test.go
@@ -92,5 +92,5 @@ func TestBlockInfoDeserialization(t *testing.T) {
 
 	// Empty string is not a valid uint64 string
 	err = json.Unmarshal([]byte(`{"height":0,"time":"","chain_id":""}`), &block)
-	require.ErrorContains(t, err, "invalid use of ,string struct tag, trying to unmarshal \"\" into uint64")
+	require.ErrorContains(t, err, "cannot unmarshal \"\" into Uint64, failed to parse integer")
 }
diff --git a/types/types.go b/types/types.go
index a8a8548c9..bd00713cf 100644
--- a/types/types.go
+++ b/types/types.go
@@ -2,9 +2,50 @@ package types
 
 import (
 	"encoding/json"
+	"fmt"
 	"strconv"
 )
 
+// Uint64 is a wrapper for uint64, but it is marshalled to and from JSON as a string
+type Uint64 uint64
+
+func (u Uint64) MarshalJSON() ([]byte, error) {
+	return json.Marshal(strconv.FormatUint(uint64(u), 10))
+}
+
+func (u *Uint64) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return fmt.Errorf("cannot unmarshal %s into Uint64, expected string-encoded integer", data)
+	}
+	v, err := strconv.ParseUint(s, 10, 64)
+	if err != nil {
+		return fmt.Errorf("cannot unmarshal %s into Uint64, failed to parse integer", data)
+	}
+	*u = Uint64(v)
+	return nil
+}
+
+// Int64 is a wrapper for int64, but it is marshalled to and from JSON as a string
+type Int64 int64
+
+func (i Int64) MarshalJSON() ([]byte, error) {
+	return json.Marshal(strconv.FormatInt(int64(i), 10))
+}
+
+func (i *Int64) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return fmt.Errorf("cannot unmarshal %s into Int64, expected string-encoded integer", data)
+	}
+	v, err := strconv.ParseInt(s, 10, 64)
+	if err != nil {
+		return fmt.Errorf("cannot unmarshal %s into Int64, failed to parse integer", data)
+	}
+	*i = Int64(v)
+	return nil
+}
+
 // HumanAddress is a printable (typically bech32 encoded) address string. Just use it as a label for developers.
 type HumanAddress = string
 
diff --git a/types/types_test.go b/types/types_test.go
new file mode 100644
index 000000000..af1d472e5
--- /dev/null
+++ b/types/types_test.go
@@ -0,0 +1,86 @@
+package types
+
+import (
+	"encoding/json"
+	"math"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestUint64JSON(t *testing.T) {
+	var u Uint64
+
+	// test unmarshal
+	err := json.Unmarshal([]byte(`"123"`), &u)
+	require.NoError(t, err)
+	require.Equal(t, uint64(123), uint64(u))
+	// test marshal
+	bz, err := json.Marshal(u)
+	require.NoError(t, err)
+	require.Equal(t, `"123"`, string(bz))
+
+	// test max value unmarshal
+	err = json.Unmarshal([]byte(`"18446744073709551615"`), &u)
+	require.NoError(t, err)
+	require.Equal(t, uint64(math.MaxUint64), uint64(u))
+	// test max value marshal
+	bz, err = json.Marshal(Uint64(uint64(math.MaxUint64)))
+	require.NoError(t, err)
+	require.Equal(t, `"18446744073709551615"`, string(bz))
+
+	// test max value + 1
+	err = json.Unmarshal([]byte(`"18446744073709551616"`), &u)
+	require.Error(t, err)
+
+	// test unquoted unmarshal
+	err = json.Unmarshal([]byte(`123`), &u)
+	require.EqualError(t, err, "cannot unmarshal 123 into Uint64, expected string-encoded integer")
+
+	// test empty string
+	err = json.Unmarshal([]byte(`""`), &u)
+	require.EqualError(t, err, "cannot unmarshal \"\" into Uint64, failed to parse integer")
+}
+
+func TestInt64JSON(t *testing.T) {
+	var i Int64
+
+	// test unmarshal
+	err := json.Unmarshal([]byte(`"-123"`), &i)
+	require.NoError(t, err)
+	require.Equal(t, int64(-123), int64(i))
+	// test marshal
+	bz, err := json.Marshal(i)
+	require.NoError(t, err)
+	require.Equal(t, `"-123"`, string(bz))
+
+	// test max value unmarshal
+	err = json.Unmarshal([]byte(`"9223372036854775807"`), &i)
+	require.NoError(t, err)
+	require.Equal(t, int64(math.MaxInt64), int64(i))
+	// test max value marshal
+	bz, err = json.Marshal(Int64(int64(math.MaxInt64)))
+	require.NoError(t, err)
+	require.Equal(t, `"9223372036854775807"`, string(bz))
+
+	// test max value + 1
+	err = json.Unmarshal([]byte(`"9223372036854775808"`), &i)
+	require.Error(t, err)
+
+	// test min value unmarshal
+	err = json.Unmarshal([]byte(`"-9223372036854775808"`), &i)
+	require.NoError(t, err)
+	require.Equal(t, int64(math.MinInt64), int64(i))
+	// test min value marshal
+	bz, err = json.Marshal(Int64(int64(math.MinInt64)))
+	require.NoError(t, err)
+	require.Equal(t, `"-9223372036854775808"`, string(bz))
+
+	// test unquoted unmarshal
+	err = json.Unmarshal([]byte(`-123`), &i)
+	require.EqualError(t, err, "cannot unmarshal -123 into Int64, expected string-encoded integer")
+
+	// test empty string
+	err = json.Unmarshal([]byte(`""`), &i)
+	require.EqualError(t, err, "cannot unmarshal \"\" into Int64, failed to parse integer")
+}