diff --git a/src/GitHubMilestoneCleaner.Tests/IssueGroupEngineTests.cs b/src/GitHubMilestoneCleaner.Tests/IssueGroupEngineTests.cs
index 2b244d1..c418cdf 100644
--- a/src/GitHubMilestoneCleaner.Tests/IssueGroupEngineTests.cs
+++ b/src/GitHubMilestoneCleaner.Tests/IssueGroupEngineTests.cs
@@ -11,7 +11,7 @@ public class IssueGroupEngineTests
     public class MockIssueWrapper(string title, int number) : IssueGroupEngine.IIssueWrapper
     {
         public string Title { get; } = title;
-        public int Number { get; } = number;
+        public long Number { get; } = number;
         public Issue BackingIssue { get; } = new();
     }
 
diff --git a/src/GitHubMilestoneCleaner/Commands/AutoCleanupCommand.cs b/src/GitHubMilestoneCleaner/Commands/AutoCleanupCommand.cs
index 6691f7d..7cebbd4 100644
--- a/src/GitHubMilestoneCleaner/Commands/AutoCleanupCommand.cs
+++ b/src/GitHubMilestoneCleaner/Commands/AutoCleanupCommand.cs
@@ -164,7 +164,7 @@ public IssueWrapper(Issue issue)
         }
 
         public string Title => BackingIssue.Title;
-        public int Number => BackingIssue.Number;
+        public long Number => BackingIssue.Number;
         public Issue BackingIssue { get; }
     }
 }
\ No newline at end of file
diff --git a/src/GitHubMilestoneCleaner/Engines/IssueGroupEngine.cs b/src/GitHubMilestoneCleaner/Engines/IssueGroupEngine.cs
index e05f19e..03c0933 100644
--- a/src/GitHubMilestoneCleaner/Engines/IssueGroupEngine.cs
+++ b/src/GitHubMilestoneCleaner/Engines/IssueGroupEngine.cs
@@ -66,7 +66,7 @@ public record IssueGroup
     public interface IIssueWrapper
     {
         string Title { get; }
-        int Number { get; }
+        long Number { get; }
         Issue BackingIssue { get; }
     }
 }