diff --git a/weed/s3api/auth_signature_v4.go b/weed/s3api/auth_signature_v4.go
index b70b90add..adfc84653 100644
--- a/weed/s3api/auth_signature_v4.go
+++ b/weed/s3api/auth_signature_v4.go
@@ -434,6 +434,11 @@ func (iam *IdentityAccessManagement) validateSTSSessionToken(r *http.Request, se
 		Claims:       claims,               // Populate Claims for policy variable substitution
 	}
 
+	// Restore admin privileges if the session was created by an admin
+	if isAdmin, ok := claims["is_admin"].(bool); ok && isAdmin {
+		identity.Actions = append(identity.Actions, s3_constants.ACTION_ADMIN)
+	}
+
 	glog.V(2).Infof("Successfully validated STS session token for principal: %s, assumed role user: %s",
 		sessionInfo.Principal, sessionInfo.AssumedRoleUser)
 	return identity, cred, s3err.ErrNone
diff --git a/weed/s3api/s3api_sts.go b/weed/s3api/s3api_sts.go
index 1dcac3151..d8a376518 100644
--- a/weed/s3api/s3api_sts.go
+++ b/weed/s3api/s3api_sts.go
@@ -328,8 +328,19 @@ func (h *STSHandlers) handleAssumeRole(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// Prepare custom claims for the session
+	var modifyClaims func(claims *sts.STSSessionClaims)
+	if identity.isAdmin() {
+		modifyClaims = func(claims *sts.STSSessionClaims) {
+			if claims.RequestContext == nil {
+				claims.RequestContext = make(map[string]interface{})
+			}
+			claims.RequestContext["is_admin"] = true
+		}
+	}
+
 	// Generate common STS components
-	stsCreds, assumedUser, err := h.prepareSTSCredentials(roleArn, roleSessionName, durationSeconds, sessionPolicyJSON, nil)
+	stsCreds, assumedUser, err := h.prepareSTSCredentials(roleArn, roleSessionName, durationSeconds, sessionPolicyJSON, modifyClaims)
 	if err != nil {
 		h.writeSTSErrorResponse(w, r, STSErrInternalError, err)
 		return
diff --git a/weed/s3api/s3api_sts_assume_role_test.go b/weed/s3api/s3api_sts_assume_role_test.go
index e3f235f53..74890f74b 100644
--- a/weed/s3api/s3api_sts_assume_role_test.go
+++ b/weed/s3api/s3api_sts_assume_role_test.go
@@ -7,6 +7,8 @@ import (
 	"net/url"
 	"testing"
 
+	"github.com/seaweedfs/seaweedfs/weed/iam/sts"
+	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
 	"github.com/seaweedfs/seaweedfs/weed/s3api/s3err"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -55,13 +57,25 @@ func TestAssumeRole_CallerIdentityFallback(t *testing.T) {
 			Name:         "alice",
 			Account:      &AccountAdmin,
 			PrincipalArn: fmt.Sprintf("arn:aws:iam::%s:user/alice", defaultAccountID),
+			Actions:      []Action{s3_constants.ACTION_ADMIN},
 		}
 
 		// 1. Test prepareSTSCredentials with NO RoleArn (simulating the fallback logic having passed PrincipalArn)
 		// expected RoleArn passed to prepareSTSCredentials would be the caller's PrincipalArn
 		fallbackRoleArn := callerIdentity.PrincipalArn
 
-		stsCreds, assumedUser, err := stsHandlers.prepareSTSCredentials(fallbackRoleArn, "test-session", nil, "", nil)
+		// Prepare custom claims for the session (mimicking handleAssumeRole logic)
+		var modifyClaims func(claims *sts.STSSessionClaims)
+		if callerIdentity.isAdmin() {
+			modifyClaims = func(claims *sts.STSSessionClaims) {
+				if claims.RequestContext == nil {
+					claims.RequestContext = make(map[string]interface{})
+				}
+				claims.RequestContext["is_admin"] = true
+			}
+		}
+
+		stsCreds, assumedUser, err := stsHandlers.prepareSTSCredentials(fallbackRoleArn, "test-session", nil, "", modifyClaims)
 		require.NoError(t, err)
 
 		// Assertions
@@ -75,6 +89,11 @@ func TestAssumeRole_CallerIdentityFallback(t *testing.T) {
 
 		// The RoleArn in session info should match the fallback ARN (user ARN)
 		assert.Equal(t, fallbackRoleArn, sessionInfo.RoleArn)
+
+		// Verify is_admin claim is present
+		isAdmin, ok := sessionInfo.RequestContext["is_admin"].(bool)
+		assert.True(t, ok, "is_admin claim should be present")
+		assert.True(t, isAdmin, "is_admin claim should be true")
 	})
 
 	// Test case 2: Caller is an STS Assumed Role, No RoleArn