diff --git a/quantiles.c b/quantiles.c
index a579b29..f4783d4 100644
--- a/quantiles.c
+++ b/quantiles.c
@@ -138,22 +138,26 @@ static void
 update_estimate(struct Quantile *quantile, double value, double p, double rand,
                 double min_step)
 {
-  if (value > quantile->est && rand > (1.0 - p)) {
+  if (value >= quantile->est) {
+    if (rand < (1.0 - p))
+        return;
     quantile->step += quantile->sign > 0 ? min_step : -min_step;
-    quantile->est += quantile->step > 0.0 ? fabs(quantile->step) : min_step;
+    quantile->est += quantile->step > min_step ? quantile->step : min_step;
     if (quantile->est > value) {
       quantile->step += value - quantile->est;
-      quantile->est = value;
+      quantile->est = value + min_step / 4.0;
     }
     if (quantile->sign < 0 && quantile->step > min_step)
       quantile->step = min_step;
     quantile->sign = 1;
-  } else if (value < quantile->est && rand > p) {
+  } else {
+    if (rand < p)
+      return;
     quantile->step += quantile->sign < 0 ? min_step : -min_step;
-    quantile->est -= quantile->step > 0.0 ? fabs(quantile->step) : min_step;
+    quantile->est -= quantile->step > min_step ? quantile->step : min_step;
     if (quantile->est < value) {
       quantile->step += quantile->est - value;
-      quantile->est = value;
+      quantile->est = value - min_step / 4.0;
     }
     if (quantile->sign > 0 && quantile->step > min_step)
       quantile->step = min_step;
diff --git a/test/unit/quantiles.c b/test/unit/quantiles.c
index 8690780..e08801e 100644
--- a/test/unit/quantiles.c
+++ b/test/unit/quantiles.c
@@ -28,7 +28,7 @@ test_unit(void)
 {
   int i, j, k, min_k, max_k, q, r, in_order, out_order;
   QNT_Instance inst;
-  double x;
+  double x, x2;
 
   in_order = out_order = 0;
 
@@ -63,6 +63,32 @@ test_unit(void)
     QNT_Reset(inst);
     TEST_CHECK(inst->n_set == 0);
 
+    for (j = 0; j < 3; j++) {
+      QNT_Reset(inst);
+      x = (i + 950) / 1e9;
+      if (random() % 10)
+        x2 = (i + 951) / 1e9;
+      else
+        x2 = x;
+      for (k = 0; k < 1000; k++)
+        QNT_Accumulate(inst, random() % 2 ? x : x2);
+      for (k = 0; k < inst->n_quants; k++) {
+        TEST_CHECK(inst->quants[k].est > x - 0.4e-9);
+        TEST_CHECK(inst->quants[k].est < x2 + 0.4e-9);
+        TEST_CHECK(inst->quants[k].step < -15e-9);
+        TEST_CHECK(inst->quants[k].step > -1000e-9);
+        if (min_k * 2 == q && k < inst->repeat) {
+          if (x == x2) {
+            TEST_CHECK(inst->quants[k].step < -750e-9);
+            TEST_CHECK(inst->quants[k].step > -1000e-9);
+          } else {
+            TEST_CHECK(inst->quants[k].step < -350e-9);
+            TEST_CHECK(inst->quants[k].step > -600e-9);
+          }
+        }
+      }
+    }
+
     QNT_DestroyInstance(inst);
   }