diff --git a/app/vmselect/promql/transform.go b/app/vmselect/promql/transform.go
index ded21f2a9..495a174db 100644
--- a/app/vmselect/promql/transform.go
+++ b/app/vmselect/promql/transform.go
@@ -526,27 +526,22 @@ func vmrangeBucketsToLE(tss []*timeseries) []*timeseries {
 				xsPrev = xs
 				continue
 			}
-			if xs.start != xsPrev.end {
-				// check for duplicates at the start of bucket.
-				// in case of duplicate following le already exists.
-				// no need to add new one with zero values.
-				if _, ok := uniqTs[xs.startStr]; !ok {
-					uniqTs[xs.startStr] = xs.ts
-					xssNew = append(xssNew, x{
-						endStr: xs.startStr,
-						end:    xs.start,
-						ts:     copyTS(ts, xs.startStr),
-					})
-				}
+			if xs.start != xsPrev.end && uniqTs[xs.startStr] == nil {
+				uniqTs[xs.startStr] = xs.ts
+				xssNew = append(xssNew, x{
+					endStr: xs.startStr,
+					end:    xs.start,
+					ts:     copyTS(ts, xs.startStr),
+				})
 			}
 			ts.MetricName.AddTag("le", xs.endStr)
-			if prevTs, ok := uniqTs[xs.endStr]; !ok {
+			prevTs := uniqTs[xs.endStr]
+			if prevTs != nil {
+				// the end of the current bucket is not unique, need to merge it with the existing bucket.
+				mergeNonOverlappingTimeseries(prevTs, xs.ts)
+			} else {
 				xssNew = append(xssNew, xs)
 				uniqTs[xs.endStr] = xs.ts
-			} else {
-				// end of current bucket not uniq,
-				// need to merge it with existing bucket.
-				mergeNonOverlappingTimeseries(prevTs, xs.ts)
 			}
 			xsPrev = xs
 		}
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index d13dfbe76..fdfbdcd81 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -12,6 +12,7 @@
 
 * BUGFIX: vmagent: prevent from high CPU usage bug during failing scrapes with small `scrape_timeout` (less than a few seconds).
 * BUGFIX: vmagent: reduce memory usage when Kubernetes service discovery is used in big number of distinct jobs by sharing the cache. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1113
+* BUGFUX: avoid `duplicate time series` error if `prometheus_buckets()` covers a time range with distinct set of buckets.
 * BUGFIX: prevent exponent overflow when processing extremely small values close to zero such as `2.964393875E-314`. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1114