diff --git a/libs/ml/include/psemek/ml/neural_net/activation.hpp b/libs/ml/include/psemek/ml/neural_net/activation.hpp
index 7c9318ad..e4d530ef 100644
--- a/libs/ml/include/psemek/ml/neural_net/activation.hpp
+++ b/libs/ml/include/psemek/ml/neural_net/activation.hpp
@@ -11,6 +11,7 @@ namespace psemek::ml
 	//   f'(x) = G(f(x)) for some G: R -> R
 	enum class activation_type
 	{
+		id,
 		sigmoid,
 		tanh,
 		relu,
@@ -28,6 +29,8 @@ namespace psemek::ml
 	T activation(T x, activation_type type)
 	{
 		switch (type) {
+		case activation_type::id:
+			return x;
 		case activation_type::sigmoid:
 			return 1.f / (1.f + std::exp(-x));
 		case activation_type::tanh:
@@ -43,6 +46,8 @@ namespace psemek::ml
 	T activation_derivative(T value, activation_type type)
 	{
 		switch (type) {
+		case activation_type::id:
+			return T{1};
 		case activation_type::sigmoid:
 			return value * (T{1} - value);
 		case activation_type::tanh: