diff --git a/src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonObject.cs b/src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonObject.cs
index ebab8d554de25e..be00902ce449f4 100644
--- a/src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonObject.cs
+++ b/src/libraries/System.Text.Json/src/System/Text/Json/Nodes/JsonObject.cs
@@ -267,14 +267,14 @@ internal void SetItem(string propertyName, JsonNode? value)
             OrderedDictionary<string, JsonNode?> dict = Dictionary;
 
             if (
-#if NET10_0_OR_GREATER
-                !dict.TryAdd(propertyName, value, out int index)
-#else
+#if NET9_0
                 !dict.TryAdd(propertyName, value)
+#else
+                !dict.TryAdd(propertyName, value, out int index)
 #endif
                 )
             {
-#if !NET10_0_OR_GREATER
+#if NET9_0
                 int index = dict.IndexOf(propertyName);
 #endif
                 Debug.Assert(index >= 0);