why HTTPRequest from scapy module doesn't work in packet sniffer program code?

Question

this is a packet sniffer tool that I'm developing, however, my code works well and prints all sniffed data, but when I use the HTTPRequest if statement, it doesn't run, nor does it give me any errors, it just does nothing at all. However, if I remove the if statement it works, what is the reason for this?

Code:

#!usr/bin/env python

import scapy.all as scapy
from scapy.layers import http


def sniff(interface):
    scapy.sniff(iface=interface, store=False, prn=process_sniffed_packet)  # , filter="udp")


def process_sniffed_packet(packet):
    if packet.haslayer(http.HTTPRequest):      
        print(packet.show())



sniff("wlan0")