diff --git a/src/map_extras.cpp b/src/map_extras.cpp
index bf02a4b81d6e8..3e9080f333793 100644
--- a/src/map_extras.cpp
+++ b/src/map_extras.cpp
@@ -2740,14 +2740,13 @@ void apply_function( const string_id<map_extra> &id, map &m, const tripoint &abs
             break;
         }
         case map_extra_method::mapgen: {
-            tripoint over( abs_sub );
-            sm_to_omt( over );
-            mapgendata dat( over, m, 0.0f, calendar::turn, nullptr );
+            mapgendata dat( sm_to_omt_copy( abs_sub ), m, 0.0f, calendar::turn, nullptr );
             run_mapgen_func( extra.generator_id, dat );
             break;
         }
         case map_extra_method::update_mapgen: {
-            run_mapgen_update_func( extra.generator_id, sm_to_omt_copy( abs_sub ) );
+            mapgendata dat( sm_to_omt_copy( abs_sub ), m, 0.0f, calendar::start_of_cataclysm, nullptr );
+            run_mapgen_update_func( extra.generator_id, dat );
             break;
         }
         case map_extra_method::null:
diff --git a/src/mapgen.cpp b/src/mapgen.cpp
index 8af82206d208c..47ae641a37b4d 100644
--- a/src/mapgen.cpp
+++ b/src/mapgen.cpp
@@ -7752,31 +7752,37 @@ bool update_mapgen_function_json::update_map( const tripoint &omt_pos, const poi
 
     mapgendata md( omt_pos, update_tmap, 0.0f, calendar::start_of_cataclysm, miss );
 
-    // If the existing map is rotated, we need to rotate it back to the north
-    // orientation before applying our updates.
-    const int rotation = oter_get_rotation( overmap_buffer.ter( omt_pos ) );
-    if( rotation > 0 ) {
-        md.m.rotate( rotation, true );
-    }
-
-    const bool applied = update_map( md, offset, verify );
-
-    // If we rotated the map before applying updates, we now need to rotate
-    // it back to where we found it.
-    if( rotation ) {
-        md.m.rotate( 4 - rotation, true );
-    }
-
-    if( applied ) {
-        md.m.save();
-    }
-
-    return applied;
+    return update_map( md, offset, verify );
 }
 
 bool update_mapgen_function_json::update_map( mapgendata &md, const point &offset,
         const bool verify ) const
 {
+    class rotation_guard
+    {
+        public:
+            rotation_guard( const mapgendata &md )
+                : md( md ), rotation( oter_get_rotation( md.terrain_type() ) ) {
+                // If the existing map is rotated, we need to rotate it back to the north
+                // orientation before applying our updates.
+                if( rotation != 0 ) {
+                    md.m.rotate( rotation, true );
+                }
+            }
+
+            ~rotation_guard() {
+                // If we rotated the map before applying updates, we now need to rotate
+                // it back to where we found it.
+                if( rotation != 0 ) {
+                    md.m.rotate( 4 - rotation, true );
+                }
+            }
+        private:
+            const mapgendata &md;
+            const int rotation;
+    };
+    rotation_guard rot( md );
+
     for( auto &elem : setmap_points ) {
         if( verify && elem.has_vehicle_collision( md, offset ) ) {
             return false;
@@ -7831,6 +7837,16 @@ bool run_mapgen_update_func( const std::string &update_mapgen_id, const tripoint
     return update_function->second[0]->update_map( omt_pos, point_zero, miss, cancel_on_collision );
 }
 
+bool run_mapgen_update_func( const std::string &update_mapgen_id, mapgendata &dat,
+                             const bool cancel_on_collision )
+{
+    const auto update_function = update_mapgen.find( update_mapgen_id );
+    if( update_function == update_mapgen.end() || update_function->second.empty() ) {
+        return false;
+    }
+    return update_function->second[0]->update_map( dat, point_zero, cancel_on_collision );
+}
+
 std::pair<std::map<ter_id, int>, std::map<furn_id, int>> get_changed_ids_from_update(
             const std::string &update_mapgen_id )
 {
diff --git a/src/mapgen_functions.h b/src/mapgen_functions.h
index fb2994bac3233..9d23b552bca77 100644
--- a/src/mapgen_functions.h
+++ b/src/mapgen_functions.h
@@ -86,6 +86,8 @@ void place_stairs( mapgendata &dat );
 mapgen_update_func add_mapgen_update_func( const JsonObject &jo, bool &defer );
 bool run_mapgen_update_func( const std::string &update_mapgen_id, const tripoint &omt_pos,
                              mission *miss = nullptr, bool cancel_on_collision = true );
+bool run_mapgen_update_func( const std::string &update_mapgen_id, mapgendata &dat,
+                             bool cancel_on_collision = true );
 bool run_mapgen_func( const std::string &mapgen_id, mapgendata &dat );
 std::pair<std::map<ter_id, int>, std::map<furn_id, int>> get_changed_ids_from_update(
             const std::string &update_mapgen_id );