diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 6f3be85..ef1b206 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -350,6 +350,8 @@ endif()
 
 # freenull
 add_executable(freenull freenull.c)
+set_source_files_properties(freenull.c PROPERTIES COMPILE_FLAGS
+	-ULIBRESSL_INTERNAL)
 target_link_libraries(freenull ${OPENSSL_TEST_LIBS})
 add_test(freenull freenull)
 
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 26ed681..dc965bd 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -369,6 +369,7 @@ endif
 
 # freenull
 TESTS += freenull
+freenull_CPPFLAGS = $(AM_CPPFLAGS) -ULIBRESSL_INTERNAL
 check_PROGRAMS += freenull
 freenull_SOURCES = freenull.c