diff --git a/pkg/promhttputil/merge.go b/pkg/promhttputil/merge.go
index 5ebcd1389..d30f8f198 100644
--- a/pkg/promhttputil/merge.go
+++ b/pkg/promhttputil/merge.go
@@ -121,8 +121,13 @@ func MergeValues(antiAffinityBuffer model.Time, a, b model.Value, preferMax bool
 			if index, ok := fingerPrintMap[finger]; ok {
 				// Only replace if we have no value (which seems reasonable)
 				// Or we prefer max value and there is a bigger value
-				if newValue[index].Value == model.SampleValue(0) || preferMax && newValue[index].Value < item.Value {
-					newValue[index].Value = item.Value
+				existing := newValue[index]
+				if preferMax {
+					if item.Value > existing.Value {
+						newValue[index].Value = item.Value
+					}
+				} else {
+					newValue[index].Value += item.Value
 				}
 			} else {
 				newValue = append(newValue, item)
@@ -148,10 +153,14 @@ func MergeValues(antiAffinityBuffer model.Time, a, b model.Value, preferMax bool
 		addStream := func(stream *model.SampleStream) {
 			finger := stream.Metric.Fingerprint()
 
-			// If we've seen this fingerPrint before, lets make sure that a value exists
+			// If we've seen this fingerPrint before, lets make sure that a value exists and merge the streams
 			if index, ok := fingerPrintMap[finger]; ok {
-				// TODO: check this error? For now the only one is sig collision, which we check
-				newValue[index], _ = MergeSampleStream(antiAffinityBuffer, newValue[index], stream, preferMax)
+				mergedStream, err := MergeSampleStream(antiAffinityBuffer, newValue[index], stream, preferMax)
+				if err != nil {
+					// Handle merging errors (e.g., fingerprint collisions)
+					return
+				}
+				newValue[index] = mergedStream
 			} else {
 				newValue = append(newValue, stream)
 				fingerPrintMap[finger] = len(newValue) - 1
@@ -251,7 +260,27 @@ func MergeSampleStream(antiAffinityBuffer model.Time, a, b *model.SampleStream,
 		}
 
 		if !preferMax {
-			newValues = append(newValues, aValue)
+			// Summation logic
+			done := false
+
+			for i := lastOffset; i < len(b.Values); i++ {
+				bValue := b.Values[i]
+				// Check if bValue falls within antiAffinityBuffer
+				if bValue.Timestamp > (aValue.Timestamp+antiAffinityBuffer) || bValue.Timestamp < (aValue.Timestamp-antiAffinityBuffer) {
+					break
+				}
+				if bValue.Timestamp == aValue.Timestamp {
+					aValue.Value += bValue.Value // Sum overlapping values
+					done = true
+					break
+				}
+			}
+
+			if !done {
+				newValues = append(newValues, aValue)
+			} else {
+				newValues = append(newValues, aValue)
+			}
 		} else {
 			done := false