diff --git a/Chino.Android/ExposureSummary.cs b/Chino.Android/ExposureSummary.cs
index 8cc9c7d..d24f786 100644
--- a/Chino.Android/ExposureSummary.cs
+++ b/Chino.Android/ExposureSummary.cs
@@ -13,7 +13,7 @@ public PlatformExposureSummary(AndroidExposureSummary source)
         {
             AttenuationDurationsInMinutes = source.GetAttenuationDurationsInMinutes();
             DaysSinceLastExposure = source.DaysSinceLastExposure;
-            MatchedKeyCount = source.MatchedKeyCount;
+            MatchedKeyCount = (ulong)source.MatchedKeyCount;
             MaximumRiskScore = source.MaximumRiskScore;
             SummationRiskScore = source.SummationRiskScore;
         }
diff --git a/Chino.Common/ExposureSummary.cs b/Chino.Common/ExposureSummary.cs
index 4134faa..2a8cb70 100644
--- a/Chino.Common/ExposureSummary.cs
+++ b/Chino.Common/ExposureSummary.cs
@@ -24,7 +24,7 @@ public class ExposureSummary
         /// <summary>
         /// Number of matched diagnosis keys.
         /// </summary>
-        public long MatchedKeyCount { get; set; }
+        public ulong MatchedKeyCount { get; set; }
 
         /// <summary>
         /// The highest risk score of all exposure incidents, it will be a value 0-4096.
diff --git a/Chino.iOS/ExposureSummary.cs b/Chino.iOS/ExposureSummary.cs
index 065bab0..6ab3be5 100644
--- a/Chino.iOS/ExposureSummary.cs
+++ b/Chino.iOS/ExposureSummary.cs
@@ -11,7 +11,7 @@ public PlatformExposureSummary(ENExposureDetectionSummary source)
         {
             AttenuationDurationsInMinutes = source.AttenuationDurations;
             DaysSinceLastExposure = (int)source.DaysSinceLastExposure;
-            MatchedKeyCount = (long)source.MatchedKeyCount;
+            MatchedKeyCount = source.MatchedKeyCount;
             MaximumRiskScore = source.MaximumRiskScore;
             SummationRiskScore = (int)source.RiskScoreSumFullRange;
         }