diff --git a/setup.py b/setup.py
index a7fe3e4c330..5b7aae72f25 100644
--- a/setup.py
+++ b/setup.py
@@ -458,7 +458,8 @@ def detect_modules(self):
         # _json speedups
         exts.append( Extension("_json", ["_json.c"]) )
         # Python C API test module
-        exts.append( Extension('_testcapi', ['_testcapimodule.c']) )
+        exts.append( Extension('_testcapi', ['_testcapimodule.c'],
+                               depends=['testcapi_long.h']) )
         # profilers (_lsprof is for cProfile.py)
         exts.append( Extension('_hotshot', ['_hotshot.c']) )
         exts.append( Extension('_lsprof', ['_lsprof.c', 'rotatingtree.c']) )