diff --git a/api/python/arrus/devices/us4r.py b/api/python/arrus/devices/us4r.py
index 4f40c5f4b..f7b7f1398 100644
--- a/api/python/arrus/devices/us4r.py
+++ b/api/python/arrus/devices/us4r.py
@@ -117,8 +117,8 @@ def firmware_version(self):
         for i in range(self.n_us4oems):
             dev = self.get_us4oem(i)
             ver = {
-                "main": dev.get_firmware_version(),
-                "tx": dev.get_tx_firmware_version()
+                "main": f"{dev.get_firmware_version():x}",
+                "tx": f"{dev.get_tx_firmware_version():x}"
             }
             us4oem_ver.append(ver)
         result["Us4OEM"] = us4oem_ver