diff --git a/sources/ClangSharpSourceToWinmd/ClangSharpSourceWinmdGenerator.cs b/sources/ClangSharpSourceToWinmd/ClangSharpSourceWinmdGenerator.cs
index 09f053f78..ae7a795a5 100644
--- a/sources/ClangSharpSourceToWinmd/ClangSharpSourceWinmdGenerator.cs
+++ b/sources/ClangSharpSourceToWinmd/ClangSharpSourceWinmdGenerator.cs
@@ -390,7 +390,7 @@ private void EnsureEnumSizeMatchesOriginalSize(string parent, string name, IType
                         case "ULONG64":
                         case "INT64":
                         case "UINT64":
-                        case "__int64":
+                        case "__INT64":
                             nativeSize = 8;
                             break;