diff --git a/src/utils/math.hpp b/src/utils/math.hpp
index e9c1ed44f5f60..4198530f1256d 100644
--- a/src/utils/math.hpp
+++ b/src/utils/math.hpp
@@ -77,10 +77,10 @@ constexpr T modulo(T num, int mod, T min = 0)
  *  round (base_damage * bonus / divisor) to the closest integer,
  *  but up or down towards base_damage
  */
-constexpr int round_damage(int base_damage, int bonus, int divisor) {
+constexpr int round_damage(double base_damage, int bonus, int divisor) {
 	if (base_damage==0) return 0;
 	const int rounding = divisor / 2 - (bonus < divisor || divisor==1 ? 0 : 1);
-	return std::max<int>(1, (base_damage * bonus + rounding) / divisor);
+	return std::max<int>(1, static_cast<int>((base_damage * bonus + rounding) / divisor));
 }
 
 template<typename Cmp>