diff --git a/include/aidge/operator/Operator.hpp b/include/aidge/operator/Operator.hpp
index 29e340af8d83cfca00ef3d70b4cfbd26855cffde..4044992050b778005546f7b7aaba7ad76708cddb 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