diff --git a/dice.cpp b/dice.cpp
index 17193a0..427c123 100644
--- a/dice.cpp
+++ b/dice.cpp
@@ -48,6 +48,8 @@ filtered_const_roll_table::filtered_const_roll_table(const std::vector<int>& wei
 {
 	assert(weights.size() == mask.size());
 	std::vector<int> filtered;
+	filtered.reserve(mask.size());
+	indices.reserve(mask.size());
 	for (size_t i = 0; i < mask.size(); i++)
 	{
 		if (mask[i])