diff --git a/pycardium/modules/os.c b/pycardium/modules/os.c
index a693420b18979e8e1b835c85c71a943dd3c1ac9c..aa452a8dc5c573d50f144215a2d2da7bf775913a 100644
--- a/pycardium/modules/os.c
+++ b/pycardium/modules/os.c
@@ -141,7 +141,7 @@ static mp_obj_t mp_os_urandom(mp_obj_t size_in)
 	vstr_t vstr;
 
 	vstr_init_len(&vstr, size);
-	epic_trng_read((uint8_t*)vstr.buf, size);
+	epic_trng_read((uint8_t *)vstr.buf, size);
 
 	return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
 }