diff --git a/internal/serialize/keyvalues.go b/internal/serialize/keyvalues.go
index 87a29037..814a8bed 100644
--- a/internal/serialize/keyvalues.go
+++ b/internal/serialize/keyvalues.go
@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"slices"
 	"strconv"
 
 	"github.com/go-logr/logr"
@@ -144,16 +145,24 @@ func (f Formatter) formatKVs(b *bytes.Buffer, kvs ...[]interface{}) {
 			e.end = b.Len()
 			i := findObsoleteEntry(existing, e.key)
 			if i >= 0 {
-				// The old entry gets obsoleted. This ensures
-				// that if the more recent one has a different value,
-				// that value remains. If the value is the same,
-				// then we could also keep the old entry. That
-				// would lead to a more natural order of key/value
-				// pairs in the output (shared key/value in multiple
-				// log entries always at the beginning) but at the
-				// cost of another memory comparison.
-				obsolete = append(obsolete, existing[i].interval)
-				existing[i].interval = e.interval
+				data := b.Bytes()
+				if bytes.Compare(data[existing[i].start:existing[i].end], data[e.start:e.end]) == 0 {
+					// The new entry gets obsoleted because it's identical.
+					// This has the advantage that key/value pairs from
+					// a WithValues call always come first, even if the same
+					// pair gets added again later. This makes different log
+					// entries more consistent.
+					//
+					// The new entry has a higher start index and thus can be appended.
+					obsolete = append(obsolete, e.interval)
+				} else {
+					// The old entry gets obsoleted because it's value is different.
+					//
+					// Sort order is not guaranteed, we have to insert at the right place.
+					index, _ := slices.BinarySearchFunc(obsolete, existing[i].interval, func(a, b interval) int { return a.start - b.start })
+					obsolete = slices.Insert(obsolete, index, existing[i].interval)
+					existing[i].interval = e.interval
+				}
 			} else {
 				// Instead of appending at the end and doing a
 				// linear search in findEntry, we could keep
diff --git a/test/output.go b/test/output.go
index 748fcc50..ae3ed772 100644
--- a/test/output.go
+++ b/test/output.go
@@ -446,9 +446,9 @@ I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" span="
 		text:           "duplicates",
 
 		expectedOutput: `I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" span="0102030405060708" a=1
-I output.go:<LINE>] "duplicates" a=1 b=2 trace="101112131415161718191a1b1c1d1e1f" span="1112131415161718"
+I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" a=1 b=2 span="1112131415161718"
 I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" span="0102030405060708" a=1
-I output.go:<LINE>] "duplicates" a=1 c=3 trace="101112131415161718191a1b1c1d1e1f" span="2122232425262728" d=4
+I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" a=1 c=3 span="2122232425262728" d=4
 `,
 	},
 }
diff --git a/test/zapr.go b/test/zapr.go
index bc9e03ab..1e669fa5 100644
--- a/test/zapr.go
+++ b/test/zapr.go
@@ -275,9 +275,9 @@ I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" span="
 `,
 
 		`I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" span="0102030405060708" a=1
-I output.go:<LINE>] "duplicates" a=1 b=2 trace="101112131415161718191a1b1c1d1e1f" span="1112131415161718"
+I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" a=1 b=2 span="1112131415161718"
 I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" span="0102030405060708" a=1
-I output.go:<LINE>] "duplicates" a=1 c=3 trace="101112131415161718191a1b1c1d1e1f" span="2122232425262728" d=4
+I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" a=1 c=3 span="2122232425262728" d=4
 `: `{"caller":"test/output.go:<LINE>","msg":"duplicates","trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1,"v":0}
 {"caller":"test/output.go:<LINE>","msg":"duplicates","trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1,"b":2,"trace":"101112131415161718191a1b1c1d1e1f","span":"1112131415161718","v":0}
 {"caller":"test/output.go:<LINE>","msg":"duplicates","trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1,"v":0}
@@ -383,9 +383,9 @@ I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" span="
 `,
 
 		`I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" span="0102030405060708" a=1
-I output.go:<LINE>] "duplicates" a=1 b=2 trace="101112131415161718191a1b1c1d1e1f" span="1112131415161718"
+I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" a=1 b=2 span="1112131415161718"
 I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" span="0102030405060708" a=1
-I output.go:<LINE>] "duplicates" a=1 c=3 trace="101112131415161718191a1b1c1d1e1f" span="2122232425262728" d=4
+I output.go:<LINE>] "duplicates" trace="101112131415161718191a1b1c1d1e1f" a=1 c=3 span="2122232425262728" d=4
 `: `{"caller":"test/output.go:<LINE>","msg":"duplicates","v":0,"trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1}
 {"caller":"test/output.go:<LINE>","msg":"duplicates","v":0,"trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1,"b":2,"trace":"101112131415161718191a1b1c1d1e1f","span":"1112131415161718"}
 {"caller":"test/output.go:<LINE>","msg":"duplicates","v":0,"trace":"101112131415161718191a1b1c1d1e1f","span":"0102030405060708","a":1}