diff --git a/src/kernel/building.c b/src/kernel/building.c
index 3f3bf8ec1..b1a2915f9 100644
--- a/src/kernel/building.c
+++ b/src/kernel/building.c
@@ -94,7 +94,10 @@ void bt_register(building_type * type)
 
 void free_buildingtype(void *ptr) {
     building_type *btype = (building_type *)ptr;
-    free(btype->construction);
+    if (btype->construction) {
+        free(btype->construction->materials);
+        free(btype->construction);
+    }
     free(btype->_name);
     free(btype);
 }
diff --git a/src/kernel/ship.c b/src/kernel/ship.c
index a2b7c556e..6eb6116eb 100644
--- a/src/kernel/ship.c
+++ b/src/kernel/ship.c
@@ -245,7 +245,10 @@ static void free_shiptype(void *ptr) {
     ship_type *stype = (ship_type *)ptr;
     free(stype->_name);
     free(stype->coasts);
-    free(stype->construction);
+    if (stype->construction) {
+        free(stype->construction->materials);
+        free(stype->construction);
+    }
     free(stype);
 }