diff --git a/histogram.go b/histogram.go
index 0d953d5..ccb63d9 100644
--- a/histogram.go
+++ b/histogram.go
@@ -130,7 +130,7 @@ func (h *Histogram) Merge(b *Histogram) {
 			h.decimalBuckets[i] = &b
 		}
 		for j := range db {
-			h.decimalBuckets[i][j] = db[j]
+			h.decimalBuckets[i][j] += db[j]
 		}
 	}
 }