diff --git a/src/query/inc/tdigest.h b/src/query/inc/tdigest.h
index 6a89ec301db83a901b352345198480ab859c05f7..df57f983b188ced1f56a270e0620904a7ea56eb3 100644
--- a/src/query/inc/tdigest.h
+++ b/src/query/inc/tdigest.h
@@ -27,7 +27,7 @@
 #endif
 
 #define COMPRESSION 400
-#define GET_CENTROID(compression)  (ceil(compression * M_PI / 2) + 1)
+#define GET_CENTROID(compression)  (ceil(compression * M_PI / 2) + 1 + 3) // addition 3 centroid
 #define GET_THRESHOLD(compression) (7.5 + 0.37 * compression - 2e-4 * pow(compression, 2))
 #define TDIGEST_SIZE(compression)  (sizeof(TDigest) + sizeof(SCentroid)*GET_CENTROID(compression) + sizeof(SPt)*GET_THRESHOLD(compression))
 
diff --git a/src/query/src/tdigest.c b/src/query/src/tdigest.c
index 660a42e3d8228bef1c9a8ae4601474ce239ba600..c10ae020e32aa914a91d40ba165aca4d3c6ea4f4 100644
--- a/src/query/src/tdigest.c
+++ b/src/query/src/tdigest.c
@@ -78,7 +78,9 @@ static void mergeCentroid(SMergeArgs *args, SCentroid *merge) {
             args->weight_so_far / args->t->total_weight);
 
     if (k2 - args->k1 > 1 && c->weight > 0) {
-        args->idx++;
+        if(args->idx + 1 < args->t->size) { // check avoid overflow
+            args->idx++; 
+        }
         args->k1 = INTEGRATED_LOCATION(args->t->compression,
                 (args->weight_so_far - merge->weight) / args->t->total_weight);
     }