diff --git a/include/aidge/operator/Operator.hpp b/include/aidge/operator/Operator.hpp
index 982f8d81e36ab88a3e2be771fb9064b1cbf88ece..053433309cfc7e678122c7e941246e9e91c6ece9 100644
--- a/include/aidge/operator/Operator.hpp
+++ b/include/aidge/operator/Operator.hpp
@@ -53,7 +53,7 @@ enum class InputCategory : unsigned int {
 };
 
 template <>
-constexpr bool enable_bitmask_operators<InputCategory> = true;
+inline constexpr bool enable_bitmask_operators<InputCategory> = true;
 
 class Operator : public std::enable_shared_from_this<Operator> {
 protected: