diff --git a/src/character.cpp b/src/character.cpp
index c2b46774186a0..79859d300a56b 100644
--- a/src/character.cpp
+++ b/src/character.cpp
@@ -591,7 +591,7 @@ Character::Character() :
     name.clear();
     custom_profession.clear();
 
-    *path_settings = pathfinding_settings{ 0, 1000, 1000, 0, true, true, true, true, false, true };
+    *path_settings = pathfinding_settings{ 0, 1000, 1000, 0, true, true, true, true, false, true, creature_size::medium };
 
     move_mode = move_mode_walk;
     next_expected_position = std::nullopt;
diff --git a/src/map.cpp b/src/map.cpp
index 9af98479cd722..886067f0bc50e 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -10810,6 +10810,10 @@ void map::update_pathfinding_cache( const tripoint_bub_ms &p ) const
         cur_value |= PathfindingFlag::Sharp;
     }
 
+    if( terrain.has_flag( ter_furn_flag::TFLAG_SMALL_PASSAGE ) ) {
+        cur_value |= ( PathfindingFlag::RestrictLarge | PathfindingFlag::RestrictHuge );
+    }
+
     cache.special[p.x()][p.y()] = cur_value;
 }
 
diff --git a/src/mutation.cpp b/src/mutation.cpp
index fdb14e8afa4f8..25a3fe500c414 100644
--- a/src/mutation.cpp
+++ b/src/mutation.cpp
@@ -37,6 +37,7 @@
 #include "options.h"
 #include "output.h"
 #include "overmapbuffer.h"
+#include "pathfinding.h"
 #include "pimpl.h"
 #include "player_activity.h"
 #include "rng.h"
@@ -555,6 +556,7 @@ void Character::recalculate_size()
             size_class = creature_size::medium;
         }
     }
+    path_settings->size = size_class;
 }
 
 void Character::mutation_effect( const trait_id &mut, const bool worn_destroyed_override )
diff --git a/src/npc.cpp b/src/npc.cpp
index 91bdbe346c4de..a8c96021e3b12 100644
--- a/src/npc.cpp
+++ b/src/npc.cpp
@@ -261,7 +261,8 @@ npc::npc()
     patience = 0;
     attitude = NPCATT_NULL;
 
-    *path_settings = pathfinding_settings( 0, 1000, 1000, 10, true, true, true, true, false, true );
+    *path_settings = pathfinding_settings( 0, 1000, 1000, 10, true, true, true, true, false, true,
+                                           get_size() );
     for( direction threat_dir : npc_threat_dir ) {
         ai_cache.threat_map[ threat_dir ] = 0.0f;
     }
diff --git a/src/pathfinding.cpp b/src/pathfinding.cpp
index ab80eafa1fc32..2230af349baf7 100644
--- a/src/pathfinding.cpp
+++ b/src/pathfinding.cpp
@@ -228,6 +228,15 @@ int map::cost_to_pass( const tripoint_bub_ms &cur, const tripoint_bub_ms &p,
         return PF_IMPASSABLE;
     }
 
+    // RestrictTiny isn't checked since it's unclear how it would actually work as there's no category smaller than tiny
+    if( settings.size && (
+            ( p_special & PathfindingFlag::RestrictSmall && settings.size > creature_size::tiny ) ||
+            ( p_special & PathfindingFlag::RestrictMedium && settings.size > creature_size::small ) ||
+            ( p_special & PathfindingFlag::RestrictLarge && settings.size > creature_size::medium ) ||
+            ( p_special & PathfindingFlag::RestrictHuge && settings.size > creature_size::large ) ) ) {
+        return PF_IMPASSABLE;
+    }
+
     const int bash = settings.bash_strength;
     const bool allow_open_doors = settings.allow_open_doors;
     const bool allow_unlock_doors = settings.allow_unlock_doors;
@@ -296,6 +305,17 @@ int map::cost_to_pass( const tripoint_bub_ms &cur, const tripoint_bub_ms &p,
         return climb_cost;
     }
 
+    // If terrain/furniture is openable but we can't fit through the open version, ignore the tile
+    if( settings.size && allow_open_doors &&
+        ( ( terrain.open && terrain.open->has_flag( ter_furn_flag::TFLAG_SMALL_PASSAGE ) ) ||
+          ( furniture.open && furniture.open->has_flag( ter_furn_flag::TFLAG_SMALL_PASSAGE ) ) ||
+          // Windows with curtains need to be opened twice
+          ( terrain.open->open && terrain.open->open->has_flag( ter_furn_flag::TFLAG_SMALL_PASSAGE ) ) ) &&
+        settings.size > creature_size::medium
+      ) {
+        return PF_IMPASSABLE;
+    }
+
     // If it's a door and we can open it from the tile we're on, cool.
     if( allow_open_doors && ( terrain.open || furniture.open ) &&
         ( ( !terrain.has_flag( ter_furn_flag::TFLAG_OPENCLOSE_INSIDE ) &&
diff --git a/src/pathfinding.h b/src/pathfinding.h
index b744371eef444..7b83e3c49e6e1 100644
--- a/src/pathfinding.h
+++ b/src/pathfinding.h
@@ -2,9 +2,12 @@
 #ifndef CATA_SRC_PATHFINDING_H
 #define CATA_SRC_PATHFINDING_H
 
+#include <optional>
+
 #include "coords_fwd.h"
 #include "game_constants.h"
 #include "mdarray.h"
+#include "character.h"
 
 // An attribute of a particular map square that is of interest in pathfinding.
 // Has a maximum of 32 members. For more, the datatype underlying PathfindingFlags
@@ -146,14 +149,16 @@ struct pathfinding_settings {
     bool avoid_sharp = false;
     bool avoid_dangerous_fields = false;
 
+    std::optional<creature_size> size = std::nullopt;
+
     pathfinding_settings() = default;
     pathfinding_settings( const pathfinding_settings & ) = default;
 
     pathfinding_settings( int bs, int md, int ml, int cc, bool aod, bool aud, bool at, bool acs,
-                          bool art, bool as )
+                          bool art, bool as, std::optional<creature_size> sz = std::nullopt )
         : bash_strength( bs ), max_dist( md ), max_length( ml ), climb_cost( cc ),
           allow_open_doors( aod ), allow_unlock_doors( aud ), avoid_traps( at ), allow_climb_stairs( acs ),
-          avoid_rough_terrain( art ), avoid_sharp( as ) {}
+          avoid_rough_terrain( art ), avoid_sharp( as ), size( sz )  {}
 
     pathfinding_settings &operator=( const pathfinding_settings & ) = default;
 };