diff --git a/artiq/language/units.py b/artiq/language/units.py
index 23dc96f6f..c15bf7e01 100644
--- a/artiq/language/units.py
+++ b/artiq/language/units.py
@@ -215,6 +215,7 @@ def _register_unit(unit, prefixes):
 _register_unit("s", "pnum_")
 _register_unit("Hz", "_kMG")
 _register_unit("dB", "_")
+_register_unit("V", "um_k")
 
 
 def check_unit(value, unit):