diff --git a/src/script/api/script_error.cpp b/src/script/api/script_error.cpp
index a3f0e48d96..4c82dfd8bd 100644
--- a/src/script/api/script_error.cpp
+++ b/src/script/api/script_error.cpp
@@ -25,7 +25,9 @@ ScriptError::ScriptErrorMapString ScriptError::error_map_string = ScriptError::S
 
 /* static */ std::optional<std::string> ScriptError::GetLastErrorString()
 {
-	return (*error_map_string.find(ScriptError::GetLastError())).second;
+	auto it = ScriptError::error_map_string.find(ScriptError::GetLastError());
+	assert(it != ScriptError::error_map_string.end());
+	return it->second;
 }
 
 /* static */ ScriptErrorType ScriptError::StringToError(StringID internal_string_id)