Frida "invoke-virtual" method overload fails with "Error: expected a pointer"

I want to overload following method that I found by decompiling Android app with apktool:

invoke-virtual {v0, v4, v3}, Lokhttp3/aa$a;->b(Ljava/lang/String;Ljava/lang/String;)Lokhttp3/aa$a;

Here is my Frida script:

Java.perform(function() {
    var targetClass = Java.use("okhttp3.aa$a");
    targetClass.b.overload("java.lang.String", "java.lang.String").implementation = function(a, b) {
        console.log("str1:" + a);
        console.log("str2:" + b);
        return this.b(a, b);
    }
});

Hook fails with:

[ERROR] Error: expected a pointer
    at value (frida/runtime/core.js:170)
    at At (frida/node_modules/frida-java-bridge/lib/android.js:879)
    at activate (frida/node_modules/frida-java-bridge/lib/android.js:960)
    at <anonymous> (frida/node_modules/frida-java-bridge/lib/android.js:740)
    at forEach (native)
    at St (frida/node_modules/frida-java-bridge/lib/android.js:741)
    at kt (frida/node_modules/frida-java-bridge/lib/android.js:732)
    at vt (frida/node_modules/frida-java-bridge/lib/android.js:696)
    at replace (frida/node_modules/frida-java-bridge/lib/android.js:1011)
    at set (frida/node_modules/frida-java-bridge/lib/class-factory.js:1010)
    at <anonymous> (/script2.js:3)
    at <anonymous> (frida/node_modules/frida-java-bridge/lib/vm.js:16)
    at _performPendingVmOps (frida/node_modules/frida-java-bridge/index.js:238)
    at <anonymous> (frida/node_modules/frida-java-bridge/index.js:213)
    at <anonymous> (frida/node_modules/frida-java-bridge/lib/vm.js:16)
    at _performPendingVmOpsWhenReady (frida/node_modules/frida-java-bridge/index.js:232)
    at perform (frida/node_modules/frida-java-bridge/index.js:192)
    at <eval> (/script2.js:8)

How to correctly overload that method?

UPDATE

I figured out that error raised because I tried to load multiple scripts at once. Is it possible?

import frida
import sys

package_name = "com.test.com"


def hook_okhttp_url():
    hook_code = open('hook_okhttp_url.js').read()
    return hook_code


def hook_cronet_header():
    hook_code = open('hook_cronet_header.js').read()
    return hook_code


def on_message(message, data):
    if message['type'] == 'error':
        print("[ERROR] " + message['stack'])
    elif message['type'] == 'send':
        print("[INFO] " + message['payload'])
    else:
        print(message)

device = frida.get_usb_device()
process = device.attach(package_name)

okhttp_script = process.create_script(hook_okhttp_url())
cronet_script = process.create_script(hook_cronet_header())

okhttp_script.on('message', on_message)
cronet_script.on('message', on_message)

print('[*] Running Hook Test ...')

okhttp_script.load()
cronet_script.load()

sys.stdin.read()

I figured out that error raised because I tried to load multiple scripts at once. Is it possible?

Ended up with concatenating all js files with my hooks into one.