diff --git a/common/include/jukebox.h b/common/include/jukebox.h
index eb1fd7b98..115fb9cdd 100644
--- a/common/include/jukebox.h
+++ b/common/include/jukebox.h
@@ -1,9 +1,11 @@
 #ifndef __JUKEBOX_H__
 #define __JUKEBOX_H__
 
+#include "physfsx.h"
+
 #ifdef __cplusplus
 
-extern const char *const jukebox_exts[7];
+extern const file_extension_t jukebox_exts[7];
 
 void jukebox_unload();
 void jukebox_load();
diff --git a/common/include/physfsx.h b/common/include/physfsx.h
index 66cb93dd0..01be1dc24 100644
--- a/common/include/physfsx.h
+++ b/common/include/physfsx.h
@@ -327,7 +327,7 @@ static inline void PHYSFSX_readMatrix(vms_matrix *m,PHYSFS_file *file)
 #define PHYSFSX_contfile_init PHYSFSX_addRelToSearchPath
 #define PHYSFSX_contfile_close PHYSFSX_removeRelFromSearchPath
 
-typedef const char *file_extension_t;
+typedef char file_extension_t[5];
 int PHYSFSX_checkMatchingExtension(const file_extension_t *exts, const char *filename) __attribute_nonnull();
 extern int PHYSFSX_addRelToSearchPath(const char *relname, int add_to_end);
 extern int PHYSFSX_removeRelFromSearchPath(const char *relname);
diff --git a/common/main/newdemo.h b/common/main/newdemo.h
index d88cbddc0..55bd58f40 100644
--- a/common/main/newdemo.h
+++ b/common/main/newdemo.h
@@ -35,7 +35,9 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #define ND_STATE_ONEFRAMEBACKWARD	7
 
 #define DEMO_DIR                "demos/"
-#define DEMO_EXT		".dem"
+#define DEMO_EXT		"dem"
+extern const file_extension_t demo_file_extensions[2];
+
 #ifdef WORDS_BIGENDIAN
 #define DEMO_BACKUP_EXT			"386"
 #else
diff --git a/common/main/songs.h b/common/main/songs.h
index f3690a6bb..5b69d8614 100644
--- a/common/main/songs.h
+++ b/common/main/songs.h
@@ -20,12 +20,12 @@ typedef struct bim_song_info {
 #define SONG_CREDITS            4
 #define SONG_FIRST_LEVEL_SONG   5
 
-#define SONG_EXT_HMP            ".hmp"
+#define SONG_EXT_HMP            "hmp"
 #ifdef USE_SDLMIXER
-#define SONG_EXT_MID            ".mid"
-#define SONG_EXT_OGG            ".ogg"
-#define SONG_EXT_FLAC           ".flac"
-#define SONG_EXT_MP3            ".mp3"
+#define SONG_EXT_MID            "mid"
+#define SONG_EXT_OGG            "ogg"
+#define SONG_EXT_FLAC           "flac"
+#define SONG_EXT_MP3            "mp3"
 #endif
 
 int songs_play_file(const char *filename, int repeat, void (*hook_finished_track)());
diff --git a/similar/arch/sdl/jukebox.cpp b/similar/arch/sdl/jukebox.cpp
index 499ad5b7e..5c7506878 100644
--- a/similar/arch/sdl/jukebox.cpp
+++ b/similar/arch/sdl/jukebox.cpp
@@ -49,7 +49,7 @@ void jukebox_unload()
 	JukeboxSongs.num_songs = JukeboxSongs.max_songs = JukeboxSongs.max_buf = 0;
 }
 
-const char *const jukebox_exts[7] = { SONG_EXT_HMP, SONG_EXT_MID, SONG_EXT_OGG, SONG_EXT_FLAC, SONG_EXT_MP3, NULL };
+const file_extension_t jukebox_exts[7] = { SONG_EXT_HMP, SONG_EXT_MID, SONG_EXT_OGG, SONG_EXT_FLAC, SONG_EXT_MP3, "" };
 
 static int read_m3u(void)
 {
diff --git a/similar/main/menu.cpp b/similar/main/menu.cpp
index c2b62e648..6047d33e7 100644
--- a/similar/main/menu.cpp
+++ b/similar/main/menu.cpp
@@ -130,6 +130,8 @@ static void do_multi_player_menu();
 static void do_sandbox_menu();
 #endif
 
+static int select_file_recursive(const char *title, const char *orig_path, const file_extension_t *ext_list, int select_dir, int (*when_selected)(void *userdata, const char *filename), void *userdata) __attribute_nonnull();
+
 // Hide all menus
 int hide_menus(void)
 {
@@ -315,7 +317,7 @@ int RegisterPlayer()
 	const char **m;
 	char **f;
 	char **list;
-	static const char *const types[] = { ".plr", NULL };
+	static const file_extension_t types[] = { "plr", "" };
 	int i = 0, NumItems;
 	int citem = 0;
 	int allow_abort_flag = 1;
@@ -738,10 +740,9 @@ static int demo_menu_handler( listbox *lb, d_event *event, void *userdata )
 int select_demo(void)
 {
 	char **list;
-	static const char *const types[] = { DEMO_EXT, NULL };
 	int NumItems;
 
-	list = PHYSFSX_findFiles(DEMO_DIR, types);
+	list = PHYSFSX_findFiles(DEMO_DIR, demo_file_extensions);
 	if (!list)
 		return 0;	// memory error
 	if ( !*list )
@@ -1318,7 +1319,7 @@ typedef struct browser
 	void	*userdata;		// Whatever you want passed to when_selected
 	char	**list;			// All menu items
 	char	*list_buf;		// Buffer for menu item text: hopefully reduces memory fragmentation this way
-	const char	*const *ext_list;		// List of file extensions we're looking for (if looking for a music file many types are possible)
+	const file_extension_t *ext_list;		// List of file extensions we're looking for (if looking for a music file many types are possible)
 	int		select_dir;		// Allow selecting the current directory (e.g. for Jukebox level song directory)
 	int		num_files;		// Number of list items found (including parent directory and current directory if selectable)
 	int		max_files;		// How many entries we can have before having to grow the array
@@ -1363,8 +1364,6 @@ static int list_directory(browser *b)
 	return 1;
 }
 
-static int select_file_recursive(const char *title, const char *orig_path, const char *const *ext_list, int select_dir, int (*when_selected)(void *userdata, const char *filename), void *userdata);
-
 static int select_file_handler(listbox *menu, d_event *event, browser *b)
 {
 	char newpath[PATH_MAX];
@@ -1480,7 +1479,7 @@ static int select_file_handler(listbox *menu, d_event *event, browser *b)
 	return 0;
 }
 
-static int select_file_recursive(const char *title, const char *orig_path, const char *const *ext_list, int select_dir, int (*when_selected)(void *userdata, const char *filename), void *userdata)
+static int select_file_recursive(const char *title, const char *orig_path, const file_extension_t *ext_list, int select_dir, int (*when_selected)(void *userdata, const char *filename), void *userdata)
 {
 	browser *b;
 	const char *sep = PHYSFS_getDirSeparator();
@@ -1681,7 +1680,7 @@ static int sound_menuset(newmenu *menu, d_event *event, void *userdata)
 #ifdef USE_SDLMIXER
 			if (citem == opt_sm_mtype3_lmpath)
 			{
-				static const char *const ext_list[] = { ".m3u", NULL };		// select a directory or M3U playlist
+				static const file_extension_t ext_list[] = { "m3u", "" };		// select a directory or M3U playlist
 				select_file_recursive(
 #ifndef _WIN32
 					"Select directory or\nM3U playlist to\n play level music from",
diff --git a/similar/main/newdemo.cpp b/similar/main/newdemo.cpp
index 93f214d88..996e004ac 100644
--- a/similar/main/newdemo.cpp
+++ b/similar/main/newdemo.cpp
@@ -163,6 +163,8 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #define DEMO_MAX_LEVELS				29
 
+const file_extension_t demo_file_extensions[2] = { DEMO_EXT, "" };
+
 // In- and Out-files
 PHYSFS_file *infile;
 PHYSFS_file *outfile = NULL;
@@ -3730,10 +3732,9 @@ try_again:
 int newdemo_count_demos()
 {
 	char **find, **i;
-	static const char *const types[] = { DEMO_EXT, NULL };
 	int NumFiles=0;
 
-	find = PHYSFSX_findFiles(DEMO_DIR, types);
+	find = PHYSFSX_findFiles(DEMO_DIR, demo_file_extensions);
 
 	for (i = find; *i != NULL; i++)
 		NumFiles++;
@@ -3757,7 +3758,6 @@ void newdemo_start_playback(const char * filename)
 	{
 		// Randomly pick a filename
 		int NumFiles = 0, RandFileNum;
-		static const char *const types[] = { DEMO_EXT, NULL };
 
 		rnd_demo = PURPOSE_RANDOM_PLAY;
 		NumFiles = newdemo_count_demos();
@@ -3769,7 +3769,7 @@ void newdemo_start_playback(const char * filename)
 		RandFileNum = d_rand() % NumFiles;
 		NumFiles = 0;
 
-		find = PHYSFSX_findFiles(DEMO_DIR, types);
+		find = PHYSFSX_findFiles(DEMO_DIR, demo_file_extensions);
 
 		for (i = find; *i != NULL; i++)
 		{
diff --git a/similar/misc/physfsx.cpp b/similar/misc/physfsx.cpp
index 8a09a00e9..c589ead12 100644
--- a/similar/misc/physfsx.cpp
+++ b/similar/misc/physfsx.cpp
@@ -19,14 +19,17 @@
 #include "object.h"
 #include "newdemo.h"
 
+static const file_extension_t archive_exts[] = { "dxa", "" };
+
 int PHYSFSX_checkMatchingExtension(const file_extension_t *exts, const char *filename)
 {
 	const char *ext = strrchr(filename, '.');
 	if (!ext)
 		return 0;
+	++ext;
 	for (const file_extension_t *k = exts;; ++k)	// see if the file is of a type we want
 	{
-		if (!*k)
+		if (!(*k)[0])
 			return 0;
 		if (!d_stricmp(ext, *k))
 			return 1;
@@ -350,7 +353,7 @@ int PHYSFSX_rename(const char *oldpath, const char *newpath)
 
 // Find files at path that have an extension listed in exts
 // The extension list exts must be NULL-terminated, with each ext beginning with a '.'
-char **PHYSFSX_findFiles(const char *path, const char *const *exts)
+char **PHYSFSX_findFiles(const char *path, const file_extension_t *exts)
 {
 	char **list = PHYSFS_enumerateFiles(path);
 	char **i, **j = list;
@@ -375,7 +378,7 @@ char **PHYSFSX_findFiles(const char *path, const char *const *exts)
 
 // Same function as above but takes a real directory as second argument, only adding files originating from this directory.
 // This can be used to further seperate files in search path but it must be made sure realpath is properly formatted.
-char **PHYSFSX_findabsoluteFiles(const char *path, const char *realpath, const char *const *exts)
+char **PHYSFSX_findabsoluteFiles(const char *path, const char *realpath, const file_extension_t *exts)
 {
 	char **list = PHYSFS_enumerateFiles(path);
 	char **i, **j = list;
@@ -480,7 +483,6 @@ PHYSFS_file *PHYSFSX_openWriteBuffered(const char *filename)
 void PHYSFSX_addArchiveContent()
 {
 	char **list = NULL;
-	static const char *const archive_exts[] = { ".dxa", NULL };
 	int i = 0, content_updated = 0;
 
 	con_printf(CON_DEBUG, "PHYSFS: Adding archives to the game.");
@@ -531,7 +533,6 @@ void PHYSFSX_addArchiveContent()
 void PHYSFSX_removeArchiveContent()
 {
 	char **list = NULL;
-	static const char *const archive_exts[] = { ".dxa", NULL };
 	int i = 0;
 
 	// find files in Searchpath ...