diff --git a/src/industry.h b/src/industry.h
--- a/src/industry.h
+++ b/src/industry.h
@@ -143,4 +143,13 @@ void ReleaseDisastersTargetingIndustry(I
 #define FOR_ALL_INDUSTRIES_FROM(var, start) FOR_ALL_ITEMS_FROM(Industry, industry_index, var, start)
 #define FOR_ALL_INDUSTRIES(var) FOR_ALL_INDUSTRIES_FROM(var, 0)
 
+/**
+ * Data for managing the number and type of industries in the game.
+ */
+struct IndustryBuildData {
+	void TryBuildNewIndustry();
+};
+
+extern IndustryBuildData _industry_builder;
+
 #endif /* INDUSTRY_H */