diff --git a/libs/util/include/psemek/util/statistics.hpp b/libs/util/include/psemek/util/statistics.hpp
index e7643125..7a747f7a 100644
--- a/libs/util/include/psemek/util/statistics.hpp
+++ b/libs/util/include/psemek/util/statistics.hpp
@@ -120,8 +120,11 @@ namespace psemek::util
 
 				base_statistics result;
 				result.count_ = s1.count_ + s2.count_;
-				result.mean_ = (s1.count_ * s1.mean_ + s2.count_ * s2.mean_) / result.count_;
-				result.variance_ = (s1.count_ * (s1.variance_ + sqr(s1.mean_ - result.mean_)) + s2.count_ * (s2.variance_ + sqr(s2.mean_ - result.mean_))) / result.count_;
+				if (result.count_ > 0)
+				{
+					result.mean_ = (s1.count_ * s1.mean_ + s2.count_ * s2.mean_) / result.count_;
+					result.variance_ = (s1.count_ * (s1.variance_ + sqr(s1.mean_ - result.mean_)) + s2.count_ * (s2.variance_ + sqr(s2.mean_ - result.mean_))) / result.count_;
+				}
 				return result;
 			}