diff --git a/common/include/editor/editor.h b/common/include/editor/editor.h
index 20c3dd4b2..beb20b355 100644
--- a/common/include/editor/editor.h
+++ b/common/include/editor/editor.h
@@ -26,6 +26,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #ifndef _EDITOR_H
 #define _EDITOR_H
 
+#include <physfs.h>
 #include "dxxsconf.h"
 #include "vecmat.h"
 #include "segment.h"
diff --git a/common/include/physfs-serial.h b/common/include/physfs-serial.h
index fa697e0c1..d6159131e 100644
--- a/common/include/physfs-serial.h
+++ b/common/include/physfs-serial.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <stdexcept>
+#include "physfsx.h"
 #include "serial.h"
 
 class PHYSFSX_short_read : public std::runtime_error
diff --git a/common/main/multiinternal.h b/common/main/multiinternal.h
index 364213a1e..76e17a5d1 100644
--- a/common/main/multiinternal.h
+++ b/common/main/multiinternal.h
@@ -6,6 +6,7 @@
  */
 #pragma once
 
+#include "dxxerror.h"
 #include "object.h"
 #include "powerup.h"
 
diff --git a/common/main/newdemo.h b/common/main/newdemo.h
index c49d06886..5cb56e6ca 100644
--- a/common/main/newdemo.h
+++ b/common/main/newdemo.h
@@ -28,6 +28,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #define _NEWDEMO_H
 
 #ifdef __cplusplus
+#include "physfsx.h"
 
 struct object;
 struct objptridx_t;
diff --git a/common/main/object.h b/common/main/object.h
index 244134121..530ddcd4a 100644
--- a/common/main/object.h
+++ b/common/main/object.h
@@ -35,6 +35,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "laser.h"
 
 #ifdef __cplusplus
+#include <cassert>
 #include <cstdint>
 #include "dxxsconf.h"
 #include "compiler-array.h"
diff --git a/common/main/piggy.h b/common/main/piggy.h
index cf082e360..dabdeb161 100644
--- a/common/main/piggy.h
+++ b/common/main/piggy.h
@@ -26,7 +26,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #ifndef _PIGGY_H
 #define _PIGGY_H
 
-#include "physfsx.h"
+#include <physfs.h>
 #include "sounds.h"
 #include "hash.h"
 #include "inferno.h"
diff --git a/common/main/segment.h b/common/main/segment.h
index a693c7b38..bed090e00 100644
--- a/common/main/segment.h
+++ b/common/main/segment.h
@@ -26,17 +26,20 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #ifndef _SEGMENT_H
 #define _SEGMENT_H
 
-#include "physfsx.h"
+#include <physfs.h>
 #include "pstypes.h"
 #include "maths.h"
 #include "vecmat.h"
 #include "dxxsconf.h"
 
 #ifdef __cplusplus
+#include <cassert>
 #include <cstdint>
 #include <stdexcept>
 #include "countarray.h"
 
+#include "compiler-type_traits.h"
+
 // Version 1 - Initial version
 // Version 2 - Mike changed some shorts to bytes in segments, so incompatible!
 
diff --git a/common/main/switch.h b/common/main/switch.h
index dc679f4e7..5e4063065 100644
--- a/common/main/switch.h
+++ b/common/main/switch.h
@@ -26,6 +26,8 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #ifndef _SWITCH_H
 #define _SWITCH_H
 
+#include <physfs.h>
+
 #ifdef __cplusplus
 #include "pack.h"
 
diff --git a/common/main/vclip.h b/common/main/vclip.h
index 19e8fa55f..beadcc7b1 100644
--- a/common/main/vclip.h
+++ b/common/main/vclip.h
@@ -29,7 +29,6 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #include "gr.h"
 #include "piggy.h"
-#include "physfsx.h"
 
 #ifdef __cplusplus
 #include "dxxsconf.h"
diff --git a/common/main/wall.h b/common/main/wall.h
index 0158df48a..fbdce696f 100644
--- a/common/main/wall.h
+++ b/common/main/wall.h
@@ -26,6 +26,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #ifndef _WALL_H
 #define _WALL_H
 
+#include <physfs.h>
 #include "segment.h"
 
 struct object;
diff --git a/common/ui/file.cpp b/common/ui/file.cpp
index b61d04e39..e6642e93c 100644
--- a/common/ui/file.cpp
+++ b/common/ui/file.cpp
@@ -19,9 +19,9 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #include <stdlib.h>
 #include <string.h>
+#include <physfs.h>
 
 #include "event.h"
-#include "physfsx.h"
 #include "maths.h"
 #include "pstypes.h"
 #include "gr.h"
diff --git a/d1x-rebirth/editor/ehostage.cpp b/d1x-rebirth/editor/ehostage.cpp
index 5a16bef7a..b4a272d86 100644
--- a/d1x-rebirth/editor/ehostage.cpp
+++ b/d1x-rebirth/editor/ehostage.cpp
@@ -29,6 +29,7 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include <string.h>
 #include <math.h>
 
+#include "dxxerror.h"
 #include "screens.h"
 #include "editor/esegment.h"
 #include "ehostage.h"
diff --git a/d1x-rebirth/main/bmread.cpp b/d1x-rebirth/main/bmread.cpp
index cfd56de1a..02525bdee 100644
--- a/d1x-rebirth/main/bmread.cpp
+++ b/d1x-rebirth/main/bmread.cpp
@@ -57,6 +57,7 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "cntrlcen.h"
 #include "args.h"
 #include "text.h"
+#include "physfsx.h"
 #include "strutil.h"
 #ifdef EDITOR
 #include "editor/texpage.h"
diff --git a/d1x-rebirth/main/custom.cpp b/d1x-rebirth/main/custom.cpp
index 5c9c920a4..8d2eb34f7 100644
--- a/d1x-rebirth/main/custom.cpp
+++ b/d1x-rebirth/main/custom.cpp
@@ -19,6 +19,7 @@
 #include "hash.h"
 #include "u_mem.h"
 #include "custom.h"
+#include "physfsx.h"
 
 //#define D2TMAP_CONV // used for testing
 
diff --git a/d2x-rebirth/main/bmread.cpp b/d2x-rebirth/main/bmread.cpp
index 20e95b7e0..08f954171 100644
--- a/d2x-rebirth/main/bmread.cpp
+++ b/d2x-rebirth/main/bmread.cpp
@@ -38,6 +38,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "u_mem.h"
 #include "dxxerror.h"
 #include "object.h"
+#include "physfsx.h"
 #include "vclip.h"
 #include "effects.h"
 #include "polyobj.h"
diff --git a/d2x-rebirth/main/movie.cpp b/d2x-rebirth/main/movie.cpp
index 14684d82a..e8e3c3355 100644
--- a/d2x-rebirth/main/movie.cpp
+++ b/d2x-rebirth/main/movie.cpp
@@ -38,6 +38,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "window.h"
 #include "console.h"
 #include "config.h"
+#include "physfsx.h"
 #include "key.h"
 #include "mouse.h"
 #include "digi.h"
diff --git a/d2x-rebirth/main/segment.cpp b/d2x-rebirth/main/segment.cpp
index 411a67f5c..90810924a 100644
--- a/d2x-rebirth/main/segment.cpp
+++ b/d2x-rebirth/main/segment.cpp
@@ -13,6 +13,7 @@
 
 
 #include "segment.h"
+#include "physfsx.h"
 
 /*
  * reads a segment2 structure from a PHYSFS_file
diff --git a/similar/2d/font.cpp b/similar/2d/font.cpp
index 39a26dca0..84358012b 100644
--- a/similar/2d/font.cpp
+++ b/similar/2d/font.cpp
@@ -38,6 +38,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "byteutil.h"
 #include "common/2d/bitmap.h"
 #include "makesig.h"
+#include "physfsx.h"
 #include "gamefont.h"
 #include "console.h"
 #include "config.h"
diff --git a/similar/arch/sdl/jukebox.cpp b/similar/arch/sdl/jukebox.cpp
index 9496a18ab..88a34fe53 100644
--- a/similar/arch/sdl/jukebox.cpp
+++ b/similar/arch/sdl/jukebox.cpp
@@ -13,7 +13,6 @@
 #include <stdio.h>
 #include <string.h>
 
-#include "physfsx.h"
 #include "hudmsg.h"
 #include "songs.h"
 #include "jukebox.h"
diff --git a/similar/arch/sdl/mouse.cpp b/similar/arch/sdl/mouse.cpp
index 2778de396..d3e81f008 100644
--- a/similar/arch/sdl/mouse.cpp
+++ b/similar/arch/sdl/mouse.cpp
@@ -19,6 +19,7 @@
 #include "window.h"
 #include "mouse.h"
 #include "playsave.h"
+#include "dxxerror.h"
 #include "args.h"
 
 static struct mouseinfo {
diff --git a/similar/editor/group.cpp b/similar/editor/group.cpp
index bfc8e531b..769f47832 100644
--- a/similar/editor/group.cpp
+++ b/similar/editor/group.cpp
@@ -35,6 +35,7 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "editor/medmisc.h"
 #include "dxxerror.h"
 #include "gamemine.h"
+#include "physfsx.h"
 #include "gameseg.h"
 #include "bm.h"				// For MAX_TEXTURES.
 #include "textures.h"
diff --git a/similar/editor/kmine.cpp b/similar/editor/kmine.cpp
index 244a0696e..4cdf61922 100644
--- a/similar/editor/kmine.cpp
+++ b/similar/editor/kmine.cpp
@@ -38,6 +38,7 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "kdefs.h"
 #include "info.h"
 #include "game.h"
+#include "physfsx.h"
 #include "gameseq.h"
 #include "object.h"
 
diff --git a/similar/editor/med.cpp b/similar/editor/med.cpp
index c57a76e7e..10d3600e0 100644
--- a/similar/editor/med.cpp
+++ b/similar/editor/med.cpp
@@ -38,6 +38,7 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "segment.h"
 #include "gr.h"
 #include "palette.h"
+#include "physfsx.h"
 #include "event.h"
 #include "window.h"
 #include "game.h"
@@ -57,7 +58,6 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "medlisp.h"
 #endif
 #include "u_mem.h"
-#include "physfsx.h"
 #include "render.h"
 #include "game.h"
 #include "gamefont.h"
diff --git a/similar/editor/mine.cpp b/similar/editor/mine.cpp
index f80cebba8..5080d38ff 100644
--- a/similar/editor/mine.cpp
+++ b/similar/editor/mine.cpp
@@ -27,7 +27,6 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include <stdlib.h>
 #include <math.h>
 #include <string.h>
-#include "physfsx.h"
 #include "key.h"
 #include "gr.h"
 #include "bm.h"			// for MAX_TEXTURES
@@ -38,6 +37,7 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "dxxerror.h"
 #include "textures.h"
 #include "object.h"
+#include "physfsx.h"
 #include "gamemine.h"
 #include "gamesave.h"
 #include "gameseg.h"
diff --git a/similar/main/ai.cpp b/similar/main/ai.cpp
index a65eb27c0..830b10052 100644
--- a/similar/main/ai.cpp
+++ b/similar/main/ai.cpp
@@ -40,6 +40,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "escort.h"
 #include "laser.h"
 #include "fvi.h"
+#include "physfsx.h"
 #include "polyobj.h"
 #include "bm.h"
 #include "weapon.h"
diff --git a/similar/main/automap.cpp b/similar/main/automap.cpp
index 7489e52cd..75d1ae4c4 100644
--- a/similar/main/automap.cpp
+++ b/similar/main/automap.cpp
@@ -58,6 +58,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "wall.h"
 #include "hostage.h"
 #include "fuelcen.h"
+#include "physfsx.h"
 #include "gameseq.h"
 #include "gamefont.h"
 #include "gameseg.h"
diff --git a/similar/main/credits.cpp b/similar/main/credits.cpp
index 6cea41b0e..6f4e66a71 100644
--- a/similar/main/credits.cpp
+++ b/similar/main/credits.cpp
@@ -49,6 +49,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "songs.h"
 #include "menu.h"
 #include "config.h"
+#include "physfsx.h"
 #if defined(DXX_BUILD_DESCENT_II)
 #include "mission.h"
 #include "gamepal.h"
diff --git a/similar/main/dumpmine.cpp b/similar/main/dumpmine.cpp
index d52516087..785815641 100644
--- a/similar/main/dumpmine.cpp
+++ b/similar/main/dumpmine.cpp
@@ -32,6 +32,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #include "pstypes.h"
 #include "console.h"
+#include "physfsx.h"
 #include "key.h"
 #include "gr.h"
 #include "palette.h"
diff --git a/similar/main/endlevel.cpp b/similar/main/endlevel.cpp
index aa36e37e6..56362784d 100644
--- a/similar/main/endlevel.cpp
+++ b/similar/main/endlevel.cpp
@@ -58,6 +58,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "wall.h"
 #include "terrain.h"
 #include "polyobj.h"
+#include "physfsx.h"
 #include "bm.h"
 #include "gameseg.h"
 #include "gameseq.h"
diff --git a/similar/main/gamefont.cpp b/similar/main/gamefont.cpp
index 21c03f0d9..13adbae82 100644
--- a/similar/main/gamefont.cpp
+++ b/similar/main/gamefont.cpp
@@ -31,6 +31,7 @@ COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include <string.h>
 #include "strutil.h"
 #include "args.h"
+#include "physfsx.h"
 #include "gamefont.h"
 #include "mission.h"
 #include "config.h"
diff --git a/similar/main/gamemine.cpp b/similar/main/gamemine.cpp
index 62c44118e..130bc7d64 100644
--- a/similar/main/gamemine.cpp
+++ b/similar/main/gamemine.cpp
@@ -38,6 +38,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "gamemine.h"
 #include "dxxerror.h"
 #include "gameseg.h"
+#include "physfsx.h"
 #include "switch.h"
 #include "game.h"
 #include "newmenu.h"
diff --git a/similar/main/kconfig.cpp b/similar/main/kconfig.cpp
index 544d86183..173172db3 100644
--- a/similar/main/kconfig.cpp
+++ b/similar/main/kconfig.cpp
@@ -38,6 +38,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "window.h"
 #include "console.h"
 #include "palette.h"
+#include "physfsx.h"
 #include "game.h"
 #include "gamefont.h"
 #include "iff.h"
diff --git a/similar/main/kmatrix.cpp b/similar/main/kmatrix.cpp
index 9f6d1ea52..6f7cbc963 100644
--- a/similar/main/kmatrix.cpp
+++ b/similar/main/kmatrix.cpp
@@ -38,6 +38,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "game.h"
 #include "gameseq.h"
 #include "window.h"
+#include "physfsx.h"
 #include "gamefont.h"
 #include "u_mem.h"
 #include "newmenu.h"
diff --git a/similar/main/newdemo.cpp b/similar/main/newdemo.cpp
index 1902642c0..06c3c6ba8 100644
--- a/similar/main/newdemo.cpp
+++ b/similar/main/newdemo.cpp
@@ -83,7 +83,6 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "mission.h"
 #include "piggy.h"
 #include "byteutil.h"
-#include "physfsx.h"
 #include "console.h"
 #include "controls.h"
 #include "playsave.h"
diff --git a/similar/main/piggy.cpp b/similar/main/piggy.cpp
index 7c114b19d..19e7e9bbd 100644
--- a/similar/main/piggy.cpp
+++ b/similar/main/piggy.cpp
@@ -43,6 +43,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "palette.h"
 #include "gamefont.h"
 #include "gamepal.h"
+#include "physfsx.h"
 #include "rle.h"
 #include "screens.h"
 #include "piggy.h"
diff --git a/similar/main/player.cpp b/similar/main/player.cpp
index c2cc7ac81..38c0ce027 100644
--- a/similar/main/player.cpp
+++ b/similar/main/player.cpp
@@ -13,6 +13,7 @@
 
 #include "player.h"
 #include "byteutil.h"
+#include "physfsx.h"
 
 
 void player_rw_swap(player_rw *p, int swap)
diff --git a/similar/main/playsave.cpp b/similar/main/playsave.cpp
index 90491229a..2bb864fd9 100644
--- a/similar/main/playsave.cpp
+++ b/similar/main/playsave.cpp
@@ -51,7 +51,6 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "makesig.h"
 #include "byteutil.h"
 #include "u_mem.h"
-#include "physfsx.h"
 #include "args.h"
 #include "vers_id.h"
 #include "newdemo.h"
diff --git a/similar/main/polyobj.cpp b/similar/main/polyobj.cpp
index fb5322734..29b358be7 100644
--- a/similar/main/polyobj.cpp
+++ b/similar/main/polyobj.cpp
@@ -36,6 +36,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "u_mem.h"
 #include "args.h"
 #include "byteutil.h"
+#include "physfsx.h"
 #ifndef DRIVE
 #include "texmap.h"
 #include "bm.h"
diff --git a/similar/main/robot.cpp b/similar/main/robot.cpp
index 67f07a3e4..408ba70b9 100644
--- a/similar/main/robot.cpp
+++ b/similar/main/robot.cpp
@@ -29,6 +29,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "robot.h"
 #include "object.h"
 #include "polyobj.h"
+#include "physfsx.h"
 
 int	N_robot_types = 0;
 int	N_robot_joints = 0;
diff --git a/similar/main/state.cpp b/similar/main/state.cpp
index 3954e1a06..0de94234a 100644
--- a/similar/main/state.cpp
+++ b/similar/main/state.cpp
@@ -73,7 +73,6 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #ifdef OGL
 #include "ogl_init.h"
 #endif
-#include "physfsx.h"
 
 #include "compiler-range_for.h"
 #include "partial_range.h"
diff --git a/similar/main/titles.cpp b/similar/main/titles.cpp
index b5a5cdfb8..808be8295 100644
--- a/similar/main/titles.cpp
+++ b/similar/main/titles.cpp
@@ -38,6 +38,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "palette.h"
 #include "iff.h"
 #include "pcx.h"
+#include "physfsx.h"
 #include "u_mem.h"
 #include "joy.h"
 #include "titles.h"
diff --git a/similar/mem/mem.cpp b/similar/mem/mem.cpp
index 88bb75526..fd96fa352 100644
--- a/similar/mem/mem.cpp
+++ b/similar/mem/mem.cpp
@@ -27,7 +27,6 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include "physfsx.h"
 #include "pstypes.h"
 #include "dxxerror.h"
 #include "args.h"
diff --git a/similar/misc/physfsx.cpp b/similar/misc/physfsx.cpp
index 50f8dcc48..6b08c5726 100644
--- a/similar/misc/physfsx.cpp
+++ b/similar/misc/physfsx.cpp
@@ -20,7 +20,6 @@
 #include <HIServices/Processes.h>
 #endif
 
-#include "physfsx.h"
 #include "args.h"
 #include "newdemo.h"
 #include "console.h"