diff --git a/tests/auto/testlib/selftests/CMakeLists.txt b/tests/auto/testlib/selftests/CMakeLists.txt
index ec321dc282..3a2def6de2 100644
--- a/tests/auto/testlib/selftests/CMakeLists.txt
+++ b/tests/auto/testlib/selftests/CMakeLists.txt
@@ -133,7 +133,7 @@ endforeach()
 list(JOIN subprograms " " subprograms)
 qt_internal_extend_target(tst_selftests
     DEFINES
-        SUBPROGRAMS=${subprograms}
+        $<$<COMPILE_LANGUAGE:CXX>:SUBPROGRAMS=${subprograms}>
 )
 # special case end