diff --git a/pytest-embedded-wokwi/pytest_embedded_wokwi/wokwi.py b/pytest-embedded-wokwi/pytest_embedded_wokwi/wokwi.py
index ed9a2858..4cdc729b 100644
--- a/pytest-embedded-wokwi/pytest_embedded_wokwi/wokwi.py
+++ b/pytest-embedded-wokwi/pytest_embedded_wokwi/wokwi.py
@@ -84,12 +84,13 @@ def _setup_simulation(self, diagram: str, firmware_path: str, elf_path: str):
         self.client.upload_file('pytest.elf', Path(elf_path))
         if firmware_path.endswith('flasher_args.json'):
             firmware = self.client.upload_idf_firmware(firmware_path)
-            self.client.start_simulation(firmware.firmware, elf='pytest.elf')
+            kwargs = {'firmware': firmware.firmware, 'elf': 'pytest.elf', 'flash_size': firmware.flash_size}
         else:
             firmware = self.client.upload_file('pytest.bin', Path(firmware_path))
-            self.client.start_simulation(firmware, elf='pytest.elf')
+            kwargs = {'firmware': firmware, 'elf': 'pytest.elf'}
 
         logging.info('Uploaded diagram and firmware to Wokwi. Starting simulation...')
+        self.client.start_simulation(**kwargs)
 
     def _start_serial_monitoring(self):
         """Start monitoring serial output and forward to stdout and message queue."""
diff --git a/pytest-embedded-wokwi/tests/test_wokwi.py b/pytest-embedded-wokwi/tests/test_wokwi.py
index 415f552e..d24e2c48 100644
--- a/pytest-embedded-wokwi/tests/test_wokwi.py
+++ b/pytest-embedded-wokwi/tests/test_wokwi.py
@@ -3,7 +3,7 @@
 import pytest
 
 wokwi_token_required = pytest.mark.skipif(
-    os.getenv('WOKWI_CLI_TOKEN') is None,
+    not os.getenv('WOKWI_CLI_TOKEN', None),
     reason='Please make sure that `WOKWI_CLI_TOKEN` env var is set. Get a token here: https://wokwi.com/dashboard/ci',
 )