diff --git a/setup.py b/setup.py
index 0f88e78..b36de5f 100644
--- a/setup.py
+++ b/setup.py
@@ -620,6 +620,8 @@
         exts.append( Extension('_testbuffer', ['_testbuffer.c']) )
         # Test loading multiple modules from one compiled file (http://bugs.python.org/issue16421)
         exts.append( Extension('_testimportmultiple', ['_testimportmultiple.c']) )
+        # Test multi-phase extension module init (PEP 489)
+        exts.append( Extension('_testmultiphase', ['_testmultiphase.c']) )
         # profiler (_lsprof is for cProfile.py)
         exts.append( Extension('_lsprof', ['_lsprof.c', 'rotatingtree.c']) )
         # static Unicode character database