diff --git a/lib/contrast.c b/lib/contrast.c
index 1f117ae..1139f01 100644
--- a/lib/contrast.c
+++ b/lib/contrast.c
@@ -116,7 +116,9 @@ int fimg_cos_01(FloatImg *s, FloatImg *d, double maxval)
 int		nbre, idx;
 double		dval;
 
+#if DEBUG_LEVEL
 fprintf(stderr, ">>> %s ( %p %p  %g )\n", __func__, s, d, maxval);
+#endif
 
 if (s->type != FIMG_TYPE_RGB) {
 	fprintf(stderr, "%s: type %d invalide\n",