diff --git a/tc/tc_red.c b/tc/tc_red.c
index 66658cac..81a83bd2 100644
--- a/tc/tc_red.c
+++ b/tc/tc_red.c
@@ -56,8 +56,11 @@ int tc_red_eval_ewma(unsigned qmin, unsigned burst, unsigned avpkt)
 	double W = 0.5;
 	double a = (double)burst + 1 - (double)qmin/avpkt;
 
-	if (a < 1.0)
+	if (a < 1.0) {
+		fprintf(stderr, "tc_red_eval_ewma() burst %u is too small ?"
+				" Try burst %u\n", burst, 1 + qmin/avpkt);
 		return -1;
+	}
 	for (wlog=1; wlog<32; wlog++, W /= 2) {
 		if (a <= (1 - pow(1-W, burst))/W)
 			return wlog;