diff --git a/doc/apple2.sgml b/doc/apple2.sgml
index ec9598d04..286acc252 100644
--- a/doc/apple2.sgml
+++ b/doc/apple2.sgml
@@ -354,6 +354,8 @@ usage.
 <item>allow_lowercase
 <item>beep
 <item>dir_entry_count
+<item>file_set_auxtype
+<item>file_set_type
 <item>get_tv
 <item>get_ostype
 <item>gmtime_dt
diff --git a/doc/apple2enh.sgml b/doc/apple2enh.sgml
index 1e94d3b60..c2076923a 100644
--- a/doc/apple2enh.sgml
+++ b/doc/apple2enh.sgml
@@ -333,6 +333,8 @@ usage.
 <item>_datetime
 <item>beep
 <item>dir_entry_count
+<item>file_set_auxtype
+<item>file_set_type
 <item>get_tv
 <item>get_ostype
 <item>gmtime_dt
diff --git a/doc/funcref.sgml b/doc/funcref.sgml
index 6561c13ec..013389b06 100644
--- a/doc/funcref.sgml
+++ b/doc/funcref.sgml
@@ -98,6 +98,8 @@ function.
 <item>allow_lowercase
 <item><ref id="beep" name="beep">
 <item><ref id="dir_entry_count" name="dir_entry_count">
+<item><ref id="file_set_type" name="file_set_type">
+<item><ref id="file_set_auxtype" name="file_set_auxtype">
 <item><ref id="get_tv" name="get_tv">
 <item><ref id="get_ostype" name="get_ostype">
 <item><ref id="gmtime_dt" name="gmtime_dt">
@@ -114,6 +116,8 @@ function.
 <item>_dos_type
 <item><ref id="beep" name="beep">
 <item><ref id="dir_entry_count" name="dir_entry_count">
+<item><ref id="file_set_type" name="file_set_type">
+<item><ref id="file_set_auxtype" name="file_set_auxtype">
 <item><ref id="get_tv" name="get_tv">
 <item><ref id="get_ostype" name="get_ostype">
 <item><ref id="gmtime_dt" name="gmtime_dt">
@@ -4267,6 +4271,48 @@ file may have unpredictable results.
 </quote>
 
 
+<sect1>file_set_auxtype<label id="file_set_auxtype"><p>
+
+<quote>
+<descrip>
+<tag/Function/Updates the ProDOS auxiliary type of a file.
+<tag/Header/<tt/<ref id="apple2.h" name="apple2.h">/
+<tag/Declaration/<tt/int __fastcall__ file_set_auxtype(const char *pathname, unsigned int auxtype);/
+<tag/Description/<tt/file_set_auxtype/ is machine dependent and does not exist for
+all supported targets. It updates the ProDOS auxiliary
+type of the <tt/pathname/ file, and returns 0 on success
+or sets <tt/errno/ on error.
+<tag/Notes/<itemize>
+<item>The function does not exist on all platforms.
+<item>See <tt/apple2_filetype.h/ for a list of known auxtypes.
+</itemize>
+<tag/Availability/cc65 (not all platforms)
+<tag/Example/None.
+</descrip>
+</quote>
+
+
+<sect1>file_set_type<label id="file_set_type"><p>
+
+<quote>
+<descrip>
+<tag/Function/Updates the ProDOS type of a file.
+<tag/Header/<tt/<ref id="apple2.h" name="apple2.h">/
+<tag/Declaration/<tt/int __fastcall__ file_set_type(const char *pathname, unsigned char type);/
+<tag/Description/<tt/file_set_type/ is machine dependent and does not exist for
+all supported targets. It updates the ProDOS type of the
+<tt/pathname/ file, and returns 0 on success or sets
+<tt/errno/ on error.
+<tag/Notes/<itemize>
+<item>The function does not exist on all platforms.
+<item>See <tt/apple2_filetype.h/ for a list of known file types.
+</itemize>
+<tag/Availability/cc65 (not all platforms)
+<tag/Example/None.
+</descrip>
+</quote>
+
+
 <sect1>free<label id="free"><p>
 
 <quote>
diff --git a/include/apple2.h b/include/apple2.h
index 82f8dd3e4..c5e2316e5 100644
--- a/include/apple2.h
+++ b/include/apple2.h
@@ -294,6 +294,12 @@ unsigned char get_tv (void);
 unsigned char get_ostype (void);
 /* Get the machine type. Returns one of the APPLE_xxx codes. */
 
+int __fastcall__ file_set_type(const char *pathname, unsigned char type);
+/* Sets the ProDOS type for the file, returns 0 on success, sets errno on failure */
+
+int __fastcall__ file_set_auxtype(const char *pathname, unsigned int auxtype);
+/* Sets the ProDOS auxtype for the file, returns 0 on success, sets errno on failure */
+
 void rebootafterexit (void);
 /* Reboot machine after program termination has completed. */
 
diff --git a/include/apple2_filetype.h b/include/apple2_filetype.h
index 83a44f532..dc15a929d 100644
--- a/include/apple2_filetype.h
+++ b/include/apple2_filetype.h
@@ -318,5 +318,7 @@
 extern unsigned char _filetype;  /* Default: PRODOS_T_BIN */
 extern unsigned int _auxtype;    /* Default: 0            */
 
+
+
 /* End of apple2_filetype.h */
 #endif
diff --git a/libsrc/apple2/file_set_info.s b/libsrc/apple2/file_set_info.s
new file mode 100644
index 000000000..1e3cde9f8
--- /dev/null
+++ b/libsrc/apple2/file_set_info.s
@@ -0,0 +1,79 @@
+;
+; Colin Leroy-Mira, 2025 <colin@colino.net>
+;
+; int __fastcall__ file_set_type(const char *pathname, unsigned char type);
+; int __fastcall__ file_set_auxtype(const char *pathname, unsigned int auxtype);
+;
+
+        .export         _file_set_type, _file_set_auxtype
+        .import         pushname, popname, mli_file_info_direct
+        .import         popa, popax
+        .include        "zeropage.inc"
+        .include        "errno.inc"
+        .include        "mli.inc"
+
+auxtype        = tmp1
+type           = tmp3
+mod_flag       = tmp4
+
+UPDATE_TYPE    = $00
+UPDATE_AUXTYPE = $FF
+
+_file_set_type:
+        sta     type
+        ldy     #UPDATE_TYPE
+        sty     mod_flag
+        beq     mli_update
+_file_set_auxtype:
+        sta     auxtype
+        stx     auxtype+1
+        ldy     #UPDATE_AUXTYPE
+        sty     mod_flag
+
+mli_update:
+        ; Get pathname
+        jsr     popax
+        jsr     pushname
+        bne     oserr
+
+        ; ProDOS 8 TechRef, 4.4.4: You should use
+        ; the GET_FILE_INFO call to read a file’s
+        ; attributes into a parameter list, modify
+        ; them as needed, and then use the same
+        ; parameter list for the SET_FILE_INFO call.
+        jsr     mli_file_info_direct
+        ; Bail if we could not get the information.
+        bcs     cleanup
+
+        ; Update type if needed
+        bit     mod_flag
+        bmi     :+
+        lda     type
+        sta     mliparam + MLI::INFO::FILE_TYPE
+        jmp     set_info
+
+:       ; Otherwise update auxtype
+        lda     auxtype
+        sta     mliparam + MLI::INFO::AUX_TYPE
+        lda     auxtype+1
+        sta     mliparam + MLI::INFO::AUX_TYPE+1
+
+set_info:
+        ; Set file information
+        lda     #SET_INFO_CALL
+        ldx     #SET_INFO_COUNT
+        jsr     callmli
+
+cleanup:
+        php                     ; Save return status
+
+        jsr     popname         ; Preserves A
+
+        plp
+        bcs     oserr
+        rts
+
+oserr:
+        jsr     ___mappederrno
+        sec
+        rts
diff --git a/libsrc/apple2/mli.inc b/libsrc/apple2/mli.inc
index 382a071b0..e28981b4a 100644
--- a/libsrc/apple2/mli.inc
+++ b/libsrc/apple2/mli.inc
@@ -20,6 +20,9 @@ DESTROY_COUNT   = 1
 RENAME_CALL     = $C2
 RENAME_COUNT    = 2
 
+SET_INFO_CALL   = $C3
+SET_INFO_COUNT  = 7
+
 GET_INFO_CALL   = $C4
 GET_INFO_COUNT  = $A