diff --git a/aws-es-proxy.go b/aws-es-proxy.go
index ae5651cc..bab082eb 100644
--- a/aws-es-proxy.go
+++ b/aws-es-proxy.go
@@ -2,7 +2,9 @@ package main
 
 import (
 	"bytes"
+	"crypto/sha256"
 	"crypto/subtle"
+	"encoding/hex"
 	"encoding/json"
 	"flag"
 	"fmt"
@@ -31,6 +33,8 @@ import (
 	"golang.org/x/net/publicsuffix"
 )
 
+const emptyBodySHA256 = "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
+
 func logger(debug bool) {
 
 	formatFilePath := func(path string) string {
@@ -285,8 +289,25 @@ func (p *proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		// Start AWS session from ENV, Shared Creds or EC2Role
 		signer := p.getSigner()
 
+		contentSha256Hash := emptyBodySHA256
+		body := replaceBody(req)
+
+		if len(body) > 0 {
+			hash, err := hexEncodedSha256(body)
+			if err != nil {
+				logrus.WithError(err).Errorln("failed to calculate hash of request body: %w", err)
+				http.Error(w, err.Error(), http.StatusBadRequest)
+				return
+			}
+
+			contentSha256Hash = hash
+		}
+
+		// Add the "X-Amz-Content-Sha256" header as required by Amazon OpenSearch Serverless.
+		req.Header.Set("X-Amz-Content-Sha256", contentSha256Hash)
+
 		// Sign the request with AWSv4
-		payload := bytes.NewReader(replaceBody(req))
+		payload := bytes.NewReader(body)
 		_, err := signer.Sign(req, payload, p.service, p.region, time.Now())
 		if err != nil {
 			p.credentials = nil
@@ -443,6 +464,15 @@ func addHeaders(src, dest http.Header) {
 	}
 }
 
+func hexEncodedSha256(b []byte) (string, error) {
+	hasher := sha256.New()
+	if _, err := hasher.Write(b); err != nil {
+		return "", fmt.Errorf("failed to write: %w", err)
+	}
+	digest := hasher.Sum(nil)
+	return hex.EncodeToString(digest), nil
+}
+
 // Signer.Sign requires a "seekable" body to sum body's sha256
 func replaceBody(req *http.Request) []byte {
 	if req.Body == nil {
diff --git a/go.mod b/go.mod
index 78cb65e5..de9e9dc7 100644
--- a/go.mod
+++ b/go.mod
@@ -3,13 +3,13 @@ module github.com/abutaha/aws-es-proxy
 go 1.20
 
 require (
-	github.com/aws/aws-sdk-go v1.44.215
+	github.com/aws/aws-sdk-go v1.47.4
 	github.com/sirupsen/logrus v1.9.0
 	go.mongodb.org/mongo-driver v1.11.2
-	golang.org/x/net v0.8.0
+	golang.org/x/net v0.17.0
 )
 
 require (
 	github.com/jmespath/go-jmespath v0.4.0 // indirect
-	golang.org/x/sys v0.6.0 // indirect
+	golang.org/x/sys v0.13.0 // indirect
 )
diff --git a/go.sum b/go.sum
index e57e12d5..e6204f92 100644
--- a/go.sum
+++ b/go.sum
@@ -1,5 +1,7 @@
 github.com/aws/aws-sdk-go v1.44.215 h1:K3KERfO6MaV349idub2w1u1H0R0KSkED0LshPnaAn3Q=
 github.com/aws/aws-sdk-go v1.44.215/go.mod h1:aVsgQcEevwlmQ7qHE9I3h+dtQgpqhFB+i8Phjh7fkwI=
+github.com/aws/aws-sdk-go v1.47.4 h1:IyhNbmPt+5ldi5HNzv7ZnXiqSglDMaJiZlzj4Yq3qnk=
+github.com/aws/aws-sdk-go v1.47.4/go.mod h1:LF8svs817+Nz+DmiMQKTO3ubZ/6IaTpq3TjupRn3Eqk=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -43,6 +45,8 @@ golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug
 golang.org/x/net v0.1.0/go.mod h1:Cx3nUiGt4eDBEyega/BKRp+/AlGL8hYe7U9odMt2Cco=
 golang.org/x/net v0.8.0 h1:Zrh2ngAOFYneWTAIAPethzeaQLuHwhuBkuV6ZiRnUaQ=
 golang.org/x/net v0.8.0/go.mod h1:QVkue5JL9kW//ek3r6jTKnTFis1tRmNAW2P1shuFdJc=
+golang.org/x/net v0.17.0 h1:pVaXccu2ozPjCXewfr1S7xza/zcXTity9cCdXQYSjIM=
+golang.org/x/net v0.17.0/go.mod h1:NxSsAGuq816PNPmqtQdLE42eU2Fs7NoRIZrHJAlaCOE=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -56,6 +60,8 @@ golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0 h1:MVltZSvRTcU2ljQOhs94SXPftV6DCNnZViHeQps87pQ=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
+golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/term v0.1.0/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=