diff --git a/shogun/structure/DualLibQPBMSOSVM.cpp b/shogun/structure/DualLibQPBMSOSVM.cpp
index 19a1d4a..abf7cd6 100644
--- a/shogun/structure/DualLibQPBMSOSVM.cpp
+++ b/shogun/structure/DualLibQPBMSOSVM.cpp
@@ -86,7 +86,7 @@ void DualLibQPBMSOSVM::init()
 	set_solver(BMRM);
 }
 
-bool DualLibQPBMSOSVM::train_machine(std::shared_ptr<Features> data)
+bool DualLibQPBMSOSVM::train_machine(const std::shared_ptr<Features>& data, const std::shared_ptr<Labels>& labs)
 {
 	require(m_model, "Model has not been set.");
 	if (!m_w)
diff --git a/shogun/structure/DualLibQPBMSOSVM.h b/shogun/structure/DualLibQPBMSOSVM.h
index 6a65b99..f42f41d 100644
--- a/shogun/structure/DualLibQPBMSOSVM.h
+++ b/shogun/structure/DualLibQPBMSOSVM.h
@@ -233,7 +233,7 @@ class DualLibQPBMSOSVM : public LinearStructuredOutputMachine
 		/** train dual SO-SVM
 		 *
 		 */
-		bool train_machine(std::shared_ptr<Features> data=NULL) override;
+		bool train_machine(const std::shared_ptr<Features>& data, const std::shared_ptr<Labels>& labs) override;
 
 	private:
 		/** init parameters