diff --git a/src/ConfigCatClient/Evaluation/RolloutEvaluator.cs b/src/ConfigCatClient/Evaluation/RolloutEvaluator.cs
index d19290f3..1d4993b3 100644
--- a/src/ConfigCatClient/Evaluation/RolloutEvaluator.cs
+++ b/src/ConfigCatClient/Evaluation/RolloutEvaluator.cs
@@ -868,7 +868,11 @@ private static string UserAttributeValueToString(object attributeValue)
         }
         else if (attributeValue.TryConvertNumericToDouble(out var number))
         {
-            return number.ToString(CultureInfo.InvariantCulture).Replace("E", "e");
+            var abs = Math.Abs(number);
+            var format = 1e-7 < abs && abs < 1e21
+                ? "0.#################"
+                : "0.#################e+0";
+            return number.ToString(format, CultureInfo.InvariantCulture);
         }
         else if (attributeValue.TryConvertDateTimeToDateTimeOffset(out var dateTimeOffset))
         {