diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 717ab9d..49c0d7c 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -56,12 +56,12 @@
         find_package(GTest REQUIRED)
     endif()
 
-    add_executable(avifgridapitest avifgridapitest.cc)
+    add_executable(avifgridapitest avifgridapitest.cc aviftest_helpers.cc)
     target_link_libraries(avifgridapitest avif ${AVIF_PLATFORM_LIBRARIES} ${GTEST_BOTH_LIBRARIES})
     target_include_directories(avifgridapitest PRIVATE ${GTEST_INCLUDE_DIRS})
     add_test(NAME avifgridapitest COMMAND avifgridapitest)
 
-    add_executable(avify4mtest avify4mtest.cc)
+    add_executable(avify4mtest avify4mtest.cc aviftest_helpers.cc)
     target_link_libraries(avify4mtest avif avif_apps ${AVIF_PLATFORM_LIBRARIES} ${GTEST_BOTH_LIBRARIES})
     target_include_directories(avify4mtest PRIVATE ${GTEST_INCLUDE_DIRS})
     add_test(NAME avify4mtest COMMAND avify4mtest)