ifconfig says "set to null" the first time

Reproduction:
1. Boot JNode
2. When eth-pci(0,3,0) device appears, do:
3. ifconfig eth-pci(0,3,0) 10.0.0.123
4. ifconfig eth-pci(0,3,0) 10.0.0.123 # again
5. ifconfig eth-pci(0,3,0) 10.0.0.124

Actual result:
Step 3: "IP address for eth-pci(0,3,0) set to null"
Step 4: "IP address for eth-pci(0,3,0) set to 10.0.0.123"
Step 5: "IP address for eth-pci(0,3,0) set to 10.0.0.123"

Obviously, the command shows the output with state *before* the interface is reconfigured.

If you insert "ifconfig" (display state only) between the commands, you see that the interface is actually configured correctly, even in Step 3 and 5, so it's the output only.

Expected result:
Step 3: "IP address for eth-pci(0,3,0) set to 10.0.0.123"
Step 4: "IP address for eth-pci(0,3,0) set to 10.0.0.123"
Step 5: "IP address for eth-pci(0,3,0) set to 10.0.0.124"

Importance:
That is very confusing.