diff --git a/test/py.twisted/Makefile.am b/test/py.twisted/Makefile.am
index 4723b7d..17baa59 100644
--- a/test/py.twisted/Makefile.am
+++ b/test/py.twisted/Makefile.am
@@ -17,7 +17,7 @@
 # under the License.
 #
 
-THRIFT = $(top_srcdir)/compiler/cpp/thrift
+THRIFT = $(top_builddir)/compiler/cpp/thrift
 
 stubs: ../ThriftTest.thrift ../SmallTest.thrift
 	$(THRIFT) --gen py:twisted ../ThriftTest.thrift