diff --git a/Source/Rbm.hpp b/Source/Rbm.hpp
index 82305b1..a0aa2a4 100644
--- a/Source/Rbm.hpp
+++ b/Source/Rbm.hpp
@@ -468,7 +468,7 @@ public:
 	void setDoLearnVariance(bool flag)
 	{
 		m_doLearnVariance = flag;
-		if (m_doLearnVariance)
+		if (m_doLearnVariance && m_batch.getSize())
 		{
 			m_variableSigma = calcSigma(m_batch.data());
 		}