diff --git a/artiq/transforms/lower_units.py b/artiq/transforms/lower_units.py
index 917a7a0cf..13c357cfa 100644
--- a/artiq/transforms/lower_units.py
+++ b/artiq/transforms/lower_units.py
@@ -1,4 +1,6 @@
 import ast
+from collections import defaultdict
+from copy import copy
 
 from artiq.language import units
 
@@ -14,6 +16,7 @@ def _add_units(f, unit_list):
 class _UnitsLowerer(ast.NodeTransformer):
     def __init__(self, rpc_map):
         self.rpc_map = rpc_map
+        self.rpc_remap = defaultdict(lambda: len(self.rpc_remap))
         self.variable_units = dict()
 
     def visit_Name(self, node):
@@ -66,9 +69,9 @@ class _UnitsLowerer(ast.NodeTransformer):
         elif node.func.id == "now":
             node.unit = "s"
         elif node.func.id == "syscall" and node.args[0].s == "rpc":
-            unit_list = [getattr(arg, "unit", None) for arg in node.args]
+            unit_list = tuple(getattr(arg, "unit", None) for arg in node.args[2:])
             rpc_n = node.args[1].n
-            self.rpc_map[rpc_n] = _add_units(self.rpc_map[rpc_n], unit_list)
+            node.args[1].n = self.rpc_remap[(rpc_n, (unit_list))]
         return node
 
     def _update_target(self, target, unit):
@@ -105,4 +108,8 @@ class _UnitsLowerer(ast.NodeTransformer):
 
 
 def lower_units(func_def, rpc_map):
-    _UnitsLowerer(rpc_map).visit(func_def)
+    ul = _UnitsLowerer(rpc_map)
+    ul.visit(func_def)
+    original_map = copy(rpc_map)
+    for (original_rpcn, unit_list), new_rpcn in ul.rpc_remap.items():
+        rpc_map[new_rpcn] = _add_units(original_map[original_rpcn], unit_list)
diff --git a/test/full_stack.py b/test/full_stack.py
index d8697b0b9..a68aa499c 100644
--- a/test/full_stack.py
+++ b/test/full_stack.py
@@ -4,6 +4,7 @@ import os
 from fractions import Fraction
 
 from artiq import *
+from artiq.language.units import Quantity
 from artiq.coredevice import comm_serial, core, runtime_exceptions, rtio
 from artiq.sim import devices as sim_devices
 
@@ -44,6 +45,7 @@ class _Primes(AutoContext):
 class _Misc(AutoContext):
     def build(self):
         self.input = 84
+        self.inhomogeneous_units = []
 
     @kernel
     def run(self):
@@ -51,6 +53,8 @@ class _Misc(AutoContext):
         decimal_fraction = Fraction("1.2")
         self.decimal_fraction_n = int(decimal_fraction.numerator)
         self.decimal_fraction_d = int(decimal_fraction.denominator)
+        self.inhomogeneous_units.append(Quantity(1000, "Hz"))
+        self.inhomogeneous_units.append(Quantity(10, "s"))
 
 
 class _PulseLogger(AutoContext):
@@ -157,6 +161,8 @@ class ExecutionCase(unittest.TestCase):
             self.assertEqual(Fraction(uut.decimal_fraction_n,
                                       uut.decimal_fraction_d),
                              Fraction("1.2"))
+            self.assertEqual(uut.inhomogeneous_units, [
+                Quantity(1000, "Hz"), Quantity(10, "s")])
 
     def test_pulses(self):
         l_device, l_host = [], []