diff --git a/nmigen/test/test_lib_cdc.py b/nmigen/test/test_lib_cdc.py
index 1f965ec0..44e8a353 100644
--- a/nmigen/test/test_lib_cdc.py
+++ b/nmigen/test/test_lib_cdc.py
@@ -21,6 +21,14 @@ def test_paramcheck(self):
         m = MultiReg(i, o, n=1)
         m = MultiReg(i, o, reset=-1)
 
+    def test_platform(self):
+        platform = lambda: None
+        platform.get_multi_reg = lambda m: "foobar{}".format(len(m._regs))
+        i = Signal()
+        o = Signal()
+        m = MultiReg(i, o, n=5)
+        self.assertEqual(m.elaborate(platform), "foobar5")
+
     def test_basic(self):
         i = Signal()
         o = Signal()
@@ -67,6 +75,13 @@ def test_paramcheck(self):
             r = ResetSynchronizer(arst, n="a")
         r = ResetSynchronizer(arst)
 
+    def test_platform(self):
+        platform = lambda: None
+        platform.get_reset_sync = lambda m: "foobar{}".format(len(m._regs))
+        arst = Signal()
+        rs = ResetSynchronizer(arst, n=6)
+        self.assertEqual(rs.elaborate(platform), "foobar6")
+
     def test_basic(self):
         arst = Signal()
         m = Module()