Calling _api/search/postquery from Modern Web Part (security validation invalid)

I am trying to call /_api/_search/postquery from a modern Script Editor web part, and I am getting this error:

VM6497:86 {"error":{"code":"-2130575251, Microsoft.SharePoint.SPException","message":{"lang":"en-US","value":"The security validation for this page is invalid and might be corrupted. Please use your web browser's Back button to try your operation again."}}}

This same code works fine in classic sharepoint web part, is there something additional I have to account for in a simple REST API call in modern?  

		var postData = {
			'request':{
			'__metadata' : {'type' : 'Microsoft.Office.Server.Search.REST.SearchRequest'},
			'Querytext' : "*",
		}}; 
		
		$.ajax({
			type: "POST",
			url : "https://mytenant.sharepoint.com/_api/search/postquery",    
			data: JSON.stringify(postData),
			headers: { 
	            "accept": "application/json;odata=verbose",
	            "content-type": "application/json;odata=verbose"
	            "X-RequestDigest": $("#__REQUESTDIGEST").val()
	        },
			success : function onSuccess(data, request){
				console.log(data);
			},
			error : function onError(error) {
				console.log(error.responseText);					
			}
		});