diff --git a/src/TechTreeImproved.cpp b/src/TechTreeImproved.cpp
index 74f85376630914e1780250a5d5144f1a83e9bb3a..84a394fd54a8d4b918f06aad6159266f8bee8314 100644
--- a/src/TechTreeImproved.cpp
+++ b/src/TechTreeImproved.cpp
@@ -119,6 +119,6 @@ const std::vector<BuildDescription> & TechTreeImproved::HowToBuild(sc2::UnitType
     else
     {
         std::cout << "No information about unit type " << sc2::UnitTypeToName(unit) << " (" << static_cast<int>(unit) << ")" << std::endl;
-        return {};
+        return empty;
     }
 }
\ No newline at end of file
diff --git a/src/TechTreeImproved.h b/src/TechTreeImproved.h
index 1c01572f890bdfb164c36e8fc2cdf9ae33be02cc..c17d847f1ebb20d46582c9927029559955ebca68 100644
--- a/src/TechTreeImproved.h
+++ b/src/TechTreeImproved.h
@@ -25,6 +25,9 @@ class TechTreeImproved
     std::map<sc2::UNIT_TYPEID, std::vector<BuildDescription>> producer_to_data;
     std::map<sc2::UNIT_TYPEID, std::vector<BuildDescription>> result_to_data;
 
+    // If there is no BuildDescription for a given type, a reference to tihs list is returned.
+    const std::vector<BuildDescription> empty {};
+
     void parse_unit(nlohmann::json::iterator it);
 public:
     TechTreeImproved();