diff --git a/src/script/api/script_base.cpp b/src/script/api/script_base.cpp
index 2472fe1c77..7fd5b2df90 100644
--- a/src/script/api/script_base.cpp
+++ b/src/script/api/script_base.cpp
@@ -44,7 +44,7 @@
 /* static */ bool ScriptBase::Chance(uint out, uint max)
 {
 	EnforcePrecondition(false, out <= max);
-	return (uint16)Rand() <= (uint16)((65535 * out) / max);
+	return ScriptBase::RandRange(max) < out;
 }
 
 /* static */ bool ScriptBase::ChanceItem(int unused_param, uint out, uint max)
diff --git a/src/script/api/script_base.hpp b/src/script/api/script_base.hpp
index a01325820f..936dee77d9 100644
--- a/src/script/api/script_base.hpp
+++ b/src/script/api/script_base.hpp
@@ -70,6 +70,7 @@ public:
 	 * @param unused_param This parameter is not used, but is needed to work with lists.
 	 * @param out How many times it should return true.
 	 * @param max Out of this many times.
+	 * @pre \a out is at most equal to \a max.
 	 * @return True if the chance worked out.
 	 */
 	static bool ChanceItem(int unused_param, uint out, uint max);