diff --git a/src/shogun/kernel/AUCKernel.cpp b/src/shogun/kernel/AUCKernel.cpp
index b5894fa20ff..d74ad72c27a 100644
--- a/src/shogun/kernel/AUCKernel.cpp
+++ b/src/shogun/kernel/AUCKernel.cpp
@@ -48,9 +48,9 @@ CLabels* CAUCKernel::setup_auc_maximization(CLabels* labels)
 	SG_INFO( "setting up AUC maximization\n") ;
 	ASSERT(labels);
 	ASSERT(labels->get_label_type() == LT_BINARY);
+	labels->ensure_valid();
 
 	// get the original labels
-	ASSERT(labels);
 	SGVector<int32_t> int_labels=((CBinaryLabels*) labels)->get_int_labels();
 	ASSERT(subkernel->get_num_vec_rhs()==int_labels.vlen);
 
diff --git a/src/shogun/kernel/SalzbergWordStringKernel.cpp b/src/shogun/kernel/SalzbergWordStringKernel.cpp
index 7459ceeb2f8..1163cf65e73 100644
--- a/src/shogun/kernel/SalzbergWordStringKernel.cpp
+++ b/src/shogun/kernel/SalzbergWordStringKernel.cpp
@@ -354,6 +354,7 @@ void CSalzbergWordStringKernel::set_prior_probs_from_labels(CLabels* labels)
 {
 	ASSERT(labels);
 	ASSERT(labels->get_label_type() == LT_BINARY);
+	labels->ensure_valid();
 
 	int32_t num_pos=0, num_neg=0;
 	for (int32_t i=0; i<labels->get_num_labels(); i++)
diff --git a/src/shogun/kernel/ScatterKernelNormalizer.h b/src/shogun/kernel/ScatterKernelNormalizer.h
index b7bcb9637f5..8c91d9f2203 100644
--- a/src/shogun/kernel/ScatterKernelNormalizer.h
+++ b/src/shogun/kernel/ScatterKernelNormalizer.h
@@ -47,6 +47,7 @@ class CScatterKernelNormalizer: public CKernelNormalizer
 		SG_REF(labels);
 		m_labels=labels;
 		ASSERT(labels->get_label_type()==LT_MULTICLASS);
+		labels->ensure_valid();
 
 		if (normalizer==NULL)
 			normalizer=new CIdentityKernelNormalizer();