diff --git a/cmake/conformance.cmake b/cmake/conformance.cmake
index 17fa4b9629..ec1f9e007d 100644
--- a/cmake/conformance.cmake
+++ b/cmake/conformance.cmake
@@ -21,6 +21,7 @@ add_custom_command(
 add_executable(conformance_test_runner
   ${protobuf_source_dir}/conformance/conformance.pb.cc
   ${protobuf_source_dir}/conformance/conformance_test.cc
+  ${protobuf_source_dir}/conformance/conformance_test_impl.cc
   ${protobuf_source_dir}/conformance/conformance_test_runner.cc
   ${protobuf_source_dir}/conformance/third_party/jsoncpp/json.h
   ${protobuf_source_dir}/conformance/third_party/jsoncpp/jsoncpp.cpp