diff --git a/Source/core/Portability.h b/Source/core/Portability.h
index 555ed55fe..23a5121de 100644
--- a/Source/core/Portability.h
+++ b/Source/core/Portability.h
@@ -849,11 +849,11 @@ namespace Core {
 
     struct EXTERNAL IUnknown : public IReferenceCounted  {
 
-        constexpr uint32_t ID_OFFSET_INTERNAL = 0x00000000;
-        constexpr uint32_t ID_OFFSET_PUBLIC   = 0x00000040;
-        constexpr uint32_t ID_OFFSET_CUSTOM   = 0x80000000;
+        static constexpr uint32_t ID_OFFSET_INTERNAL = 0x00000000;
+        static constexpr uint32_t ID_OFFSET_PUBLIC   = 0x00000040;
+        static constexpr uint32_t ID_OFFSET_CUSTOM   = 0x80000000;
 
-        constexpr uint32_t ID = (ID_OFFSET_INTERNAL + 0x0000);
+        static constexpr uint32_t ID = (ID_OFFSET_INTERNAL + 0x0000);
 
         ~IUnknown() override = default;