diff --git a/internal/encoding/json/encode.go b/internal/encoding/json/encode.go
index d5471325..63b76786 100644
--- a/internal/encoding/json/encode.go
+++ b/internal/encoding/json/encode.go
@@ -19,8 +19,6 @@ import (
 	"encoding"
 	"encoding/base64"
 	"fmt"
-	"github.com/openai/openai-go/internal/encoding/json/sentinel"
-	"github.com/openai/openai-go/internal/encoding/json/shims"
 	"math"
 	"reflect"
 	"slices"
@@ -30,6 +28,9 @@ import (
 	"unicode"
 	"unicode/utf8"
 	_ "unsafe" // for linkname
+
+	"github.com/openai/openai-go/internal/encoding/json/sentinel"
+	"github.com/openai/openai-go/internal/encoding/json/shims"
 )
 
 // Marshal returns the JSON encoding of v.
@@ -177,7 +178,7 @@ func Marshal(v any) ([]byte, error) {
 	e := newEncodeState()
 	defer encodeStatePool.Put(e)
 
-	err := e.marshal(v, encOpts{escapeHTML: true})
+	err := e.marshal(v, encOpts{escapeHTML: false})
 	if err != nil {
 		return nil, err
 	}
diff --git a/internal/requestconfig/requestconfig.go b/internal/requestconfig/requestconfig.go
index def7c58e..ac1c85ea 100644
--- a/internal/requestconfig/requestconfig.go
+++ b/internal/requestconfig/requestconfig.go
@@ -137,11 +137,13 @@ func NewRequestConfig(ctx context.Context, method string, u string, body any, ds
 	// Fallback to json serialization if none of the serialization functions that we expect
 	// to see is present.
 	if body != nil && !hasSerializationFunc {
-		content, err := json.Marshal(body)
-		if err != nil {
+		buf := new(bytes.Buffer)
+		enc := json.NewEncoder(buf)
+		enc.SetEscapeHTML(true)
+		if err := enc.Encode(body); err != nil {
 			return nil, err
 		}
-		reader = bytes.NewBuffer(content)
+		reader = buf
 	}
 
 	req, err := http.NewRequestWithContext(ctx, method, u, nil)
diff --git a/packages/param/option.go b/packages/param/option.go
index 107b58a5..d722c63e 100644
--- a/packages/param/option.go
+++ b/packages/param/option.go
@@ -3,8 +3,9 @@ package param
 import (
 	"encoding/json"
 	"fmt"
-	shimjson "github.com/openai/openai-go/internal/encoding/json"
 	"time"
+
+	shimjson "github.com/openai/openai-go/internal/encoding/json"
 )
 
 func NewOpt[T comparable](v T) Opt[T] {
@@ -62,7 +63,7 @@ func (o Opt[T]) MarshalJSON() ([]byte, error) {
 	if !o.Valid() {
 		return []byte("null"), nil
 	}
-	return json.Marshal(o.Value)
+	return shimjson.Marshal(o.Value)
 }
 
 func (o *Opt[T]) UnmarshalJSON(data []byte) error {
@@ -96,7 +97,7 @@ func (o Opt[T]) MarshalJSONWithTimeLayout(format string) []byte {
 		return nil
 	}
 
-	b, err := json.Marshal(t.Format(shimjson.TimeLayout(format)))
+	b, err := shimjson.Marshal(t.Format(shimjson.TimeLayout(format)))
 	if err != nil {
 		return nil
 	}
diff --git a/shared/constant/constants.go b/shared/constant/constants.go
index 3847a3b0..9df79f42 100644
--- a/shared/constant/constants.go
+++ b/shared/constant/constants.go
@@ -3,7 +3,7 @@
 package constant
 
 import (
-	"encoding/json"
+	shimjson "github.com/openai/openai-go/internal/encoding/json"
 )
 
 type Constant[T any] interface {
@@ -727,5 +727,5 @@ func marshalString[T ~string, PT constant[T]](v T) ([]byte, error) {
 	if v == zero {
 		v = PT(&v).Default()
 	}
-	return json.Marshal(string(v))
+	return shimjson.Marshal(string(v))
 }