diff --git a/asminc/o65.inc b/asminc/o65.inc
index 45bc7ac14..4bb9938fe 100644
--- a/asminc/o65.inc
+++ b/asminc/o65.inc
@@ -54,6 +54,14 @@ O65_HDR_ZLEN            =      22       ; Size of zp segment
 O65_HDR_STACK           =      24       ; Stacksize needed
 O65_HDR_SIZE            =      26       ; Size of header structure
 
+; Marker, magic and version number
+O65_MARKER_0            =       $01
+O65_MARKER_1            =       $00
+O65_MAGIC_0             =       $6F     ; 'o'
+O65_MAGIC_1             =       $36     ; '6'
+O65_MAGIC_2             =       $35     ; '5'
+O65_VERSION             =       $00
+
 ; Defines for the mode word
 O65_CPU_65816           =       $8000  	; Executable is for 65816
 O65_CPU_6502            =       $0000   ; Executable is for the 6502
@@ -81,6 +89,9 @@ O65_ALIGN_4             =       $0002   ; Align longwords
 O65_ALIGN_256           =       $0003   ; Align pages (256 bytes)
 O65_ALIGN_MASK          =       $0003   ; Mask to extract alignment
 
+; The mode word as generated by the ld65 linker
+O65_MODE_CC65           = O65_CPU_6502 | O65_RELOC_BYTE | O65_SIZE_16BIT | O65_FTYPE_EXE | O65_ADDR_SIMPLE | O65_ALIGN_1
+
 ; Relocation type codes
 O65_RTYPE_WORD          =       $80
 O65_RTYPE_HIGH          =       $40
diff --git a/include/o65.h b/include/o65.h
index 148b60b4e..e5957e5b6 100644
--- a/include/o65.h
+++ b/include/o65.h
@@ -52,7 +52,7 @@
 typedef unsigned o65_size;
 
 
-/* Define a structure that defines the o65 file header */
+/* Structure that defines the o65 file header */
 typedef struct o65_header o65_header;
 struct o65_header {
     char        marker[2];      /* Non-C64 marker */
@@ -72,6 +72,14 @@ struct o65_header {
 
 
 
+/* Marker, magic and version number */
+#define O65_MARKER_0            0x01
+#define O65_MARKER_1            0x00
+#define O65_MAGIC_0             0x6F    /* 'o' */
+#define O65_MAGIC_1             0x36    /* '6' */
+#define O65_MAGIC_2             0x35    /* '5' */
+#define O65_VERSION             0x00
+
 /* Defines for the mode word */
 #define O65_CPU_65816           0x8000 	/* Executable is for 65816 */
 #define O65_CPU_6502            0x0000  /* Executable is for the 6502 */
@@ -99,6 +107,14 @@ struct o65_header {
 #define O65_ALIGN_256           0x0003  /* Align pages (256 bytes) */
 #define O65_ALIGN_MASK          0x0003  /* Mask to extract alignment */
 
+/* The mode word as generated by the ld65 linker */
+#define O65_MODE_CC65           (O65_CPU_6502    |      \
+                                 O65_RELOC_BYTE  |      \
+                                 O65_SIZE_16BIT  |      \
+                                 O65_FTYPE_EXE   |      \
+                                 O65_ADDR_SIMPLE |      \
+                                 O65_ALIGN_1)
+
 /* The four o65 segment types. */
 #define O65_SEG_UNDEF  	        0x00
 #define O65_SEG_ABS	        0x01