diff --git a/tools/make_ctests.c b/tools/make_ctests.c
index 3dd99df..de3ed0e 100644
--- a/tools/make_ctests.c
+++ b/tools/make_ctests.c
@@ -117,6 +117,7 @@
     fprintf( out,
              "/* Automatically generated file; DO NOT EDIT!! */\n"
              "\n"
+             "#define WIN32_LEAN_AND_MEAN\n"
              "#include <windows.h>\n\n"
              "#define STANDALONE\n"
              "#include \"wine/test.h\"\n\n" );