diff --git a/src/strings.cpp b/src/strings.cpp
--- a/src/strings.cpp
+++ b/src/strings.cpp
@@ -1118,7 +1118,7 @@ static void FormatString(StringBuilder &
 				StringID string_id = args.GetNextParameter<StringID>();
 				if (game_script && GetStringTab(string_id) != TEXT_TAB_GAMESCRIPT_START) break;
 				/* It's prohibited for the included string to consume any arguments. */
-				StringParameters tmp_params(args, 0);
+				StringParameters tmp_params(args, game_script ? args.GetDataLeft() : 0);
 				GetStringWithArgs(builder, string_id, tmp_params, next_substr_case_index, game_script);
 				next_substr_case_index = 0;
 				break;
@@ -1138,7 +1138,7 @@ static void FormatString(StringBuilder &
 				if (game_script && size > args.GetDataLeft()) {
 					builder += "(too many parameters)";
 				} else {
-					StringParameters sub_args(args, size);
+					StringParameters sub_args(args, game_script ? args.GetDataLeft() : size);
 					GetStringWithArgs(builder, string_id, sub_args, next_substr_case_index, game_script);
 					args.AdvanceOffset(size);
 				}