diff --git a/src/base/init/lexer.l b/src/base/init/lexer.l
index 32e34bf108..6072075175 100644
--- a/src/base/init/lexer.l
+++ b/src/base/init/lexer.l
@@ -395,6 +395,7 @@ threeinch_2880		RETURN(THREEINCH_2880);
 threeinch_720		RETURN(THREEINCH_720);
 fiveinch		RETURN(FIVEINCH);
 fiveinch_360		RETURN(FIVEINCH_360);
+customdiskette		RETURN(CUSTOMDISKETTE);
 boot			RETURN(BOOT);
 sectors			RETURN(SECTORS);
 cylinders		RETURN(CYLINDERS);
diff --git a/src/base/init/parser.y b/src/base/init/parser.y
index 1f2eaac92e..f120ff1699 100644
--- a/src/base/init/parser.y
+++ b/src/base/init/parser.y
@@ -291,7 +291,7 @@ enum {
 %token L_PARTITION WHOLEDISK
 %token SECTORS CYLINDERS TRACKS HEADS OFFSET HDIMAGE HDTYPE1 HDTYPE2 HDTYPE9 DISKCYL4096
 	/* floppy */
-%token THREEINCH THREEINCH_720 THREEINCH_2880 FIVEINCH FIVEINCH_360 READONLY BOOT
+%token THREEINCH THREEINCH_720 THREEINCH_2880 FIVEINCH FIVEINCH_360 READONLY BOOT CUSTOMDISKETTE
 %token DEFAULT_DRIVES SKIP_DRIVES
 	/* ports/io */
 %token RDONLY WRONLY RDWR ORMASK ANDMASK RANGE FAST SLOW
@@ -1500,6 +1500,12 @@ floppy_flag	: READONLY              { dptr->wantrdonly = 1; }
 		| THREEINCH_720	{ dptr->default_cmos = THREE_INCH_720KFLOP; }
 		| FIVEINCH	{ dptr->default_cmos = FIVE_INCH_FLOPPY; }
 		| FIVEINCH_360	{ dptr->default_cmos = FIVE_INCH_360KFLOP; }
+		| CUSTOMDISKETTE	{ dptr->default_cmos = CUSTOM_DISKETTE; }
+		| SECTORS expression	{ dptr->sectors = $2; }
+		| CYLINDERS expression	{ dptr->tracks = $2; }
+		| TRACKS expression	{ dptr->tracks = $2; }
+		| HEADS expression		{ dptr->heads = $2; }
+		| OFFSET expression	{ dptr->header = $2; }
 		| BOOT		{ dptr->boot = 1; }
 		| L_FLOPPY string_expr
 		  {
diff --git a/src/base/misc/disks.c b/src/base/misc/disks.c
index 300e1b9a28..bf3f6a2d0e 100644
--- a/src/base/misc/disks.c
+++ b/src/base/misc/disks.c
@@ -510,7 +510,8 @@ static void image_auto(struct disk *dp)
       leavedos(19);
       return;
     }
-    if (!(set_floppy_chs_by_size(st.st_size, dp) ||
+    if (!(dp->default_cmos == CUSTOM_DISKETTE ||
+          set_floppy_chs_by_size(st.st_size, dp) ||
           set_floppy_chs_by_type(dp->default_cmos, dp)) ){
       d_printf("IMAGE auto set floppy geometry %s\n", dp->dev_name);
       leavedos(19);
@@ -685,7 +686,8 @@ static void floppy_setup(struct disk *dp)
 static void dir_auto(struct disk *dp)
 {
   if (dp->floppy) {
-    if (!set_floppy_chs_by_type(dp->default_cmos, dp))
+    if (!(dp->default_cmos == CUSTOM_DISKETTE ||
+          set_floppy_chs_by_type(dp->default_cmos, dp)))
       d_printf("DIR: Invalid floppy disk type (%d)\n", dp->default_cmos);
     else
       d_printf("DIR: Selected floppy disk type (%s)\n",
diff --git a/src/include/disks.h b/src/include/disks.h
index f183a427a9..c4a2d54d19 100644
--- a/src/include/disks.h
+++ b/src/include/disks.h
@@ -94,6 +94,7 @@ typedef enum {
   THREE_INCH_720KFLOP,		/* 3.5 in,  720 kB floppy */
   THREE_INCH_FLOPPY,		/* 3.5 in, 1.44 MB floppy */
   THREE_INCH_2880KFLOP,		/* 3.5 in, 2.88 MB floppy */
+  CUSTOM_DISKETTE,
 } floppy_t;
 
 const char *floppy_t_str(floppy_t t);