diff --git a/contrib/libtests/pngvalid.c b/contrib/libtests/pngvalid.c
index a5bdfca48..35ded08fe 100644
--- a/contrib/libtests/pngvalid.c
+++ b/contrib/libtests/pngvalid.c
@@ -11115,7 +11115,7 @@ int main(int argc, char **argv)
 #  ifdef PNG_WRITE_tRNS_SUPPORTED
       pm.test_tRNS = 1;
 #  endif
-   pm.test_lbg = 0;
+   pm.test_lbg = PNG_LIBPNG_VER >= 10600;
    pm.test_lbg_gamma_threshold = 1;
    pm.test_lbg_gamma_transform = PNG_LIBPNG_VER >= 10600;
    pm.test_lbg_gamma_sbit = 1;