diff --git a/include/aidge/operator/Operator.hpp b/include/aidge/operator/Operator.hpp
index 3a19fc702f01313bbebde7f6111f03a69e836cf3..a145aab061c714ada80728e5b6bb84ad66605e52 100644
--- a/include/aidge/operator/Operator.hpp
+++ b/include/aidge/operator/Operator.hpp
@@ -68,7 +68,7 @@ enum class InputCategory : unsigned int {
     All = static_cast<unsigned int>(-1)
 };
 template <>
-constexpr bool enable_bitmask_operators<InputCategory> = true;
+inline constexpr bool enable_bitmask_operators<InputCategory> = true;
 
 /**
  * @class Operator