diff --git a/master/cdev.c b/master/cdev.c
index a3f9be2637832427f0794212688a86a0281d4147..c349e5a39468a5910f088930d8d4cd1555454016 100644
--- a/master/cdev.c
+++ b/master/cdev.c
@@ -137,8 +137,8 @@ long eccdev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
     long retval = 0;
 
     if (master->debug_level)
-        EC_DBG("ioctl(filp = %x, cmd = %u, arg = %x)\n",
-                (u32) filp, (u32) cmd, (u32) arg);
+        EC_DBG("ioctl(filp = %x, cmd = %u (%u), arg = %x)\n",
+                (u32) filp, (u32) cmd, (u32) _IOC_NR(cmd), (u32) arg);
 
     // FIXME lock