diff --git a/libsrc/atari/cgetc.s b/libsrc/atari/cgetc.s
index cf853f5ce..54fe85bb4 100644
--- a/libsrc/atari/cgetc.s
+++ b/libsrc/atari/cgetc.s
@@ -14,7 +14,7 @@ _cgetc:
         jsr     setcursor
         lda     #12
         sta     ICAX1Z          ; fix problems with direct call to KEYBDV
-.if .not .defined(__ATARIXL__)
+.ifndef __ATARIXL__
         jsr     @1
 .else
         jsr     KEYBDV_handler
@@ -22,7 +22,7 @@ _cgetc:
         ldx     #0
         rts
 
-.if .not .defined(__ATARIXL__)
+.ifndef __ATARIXL__
 @1:     lda     KEYBDV+5
         pha
         lda     KEYBDV+4
diff --git a/libsrc/atari/crt0.s b/libsrc/atari/crt0.s
index 9bf5771d4..07f2e3be7 100644
--- a/libsrc/atari/crt0.s
+++ b/libsrc/atari/crt0.s
@@ -16,7 +16,7 @@
         .import         __STARTUP_LOAD__, __BSS_LOAD__
         .import         __RESERVED_MEMORY__
         .import         __RAM_START__, __RAM_SIZE__
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
         .import         __STACKSIZE__
         .import         sram_init
         .import         scrdev
@@ -34,7 +34,7 @@
 
         .word   $FFFF
 
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
 .segment        "MAINHDR"
 .endif
 
@@ -55,7 +55,7 @@
 
 start:
 
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
         jsr     sram_init
 .endif
 
@@ -68,7 +68,7 @@ start:
         tsx
         stx     spsave
 
-.if .not .defined(__ATARIXL__)
+.ifndef __ATARIXL__
 
 ; Report memory usage
 
@@ -101,7 +101,7 @@ start:
         jsr     initlib
 
 .if 0
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
         .import __heapadd
         .import pushax
         .import __RAM_BELOW_ROM_START__
@@ -165,7 +165,7 @@ _exit:  jsr     donelib         ; Run module destructors
         lda     APPMHI_save+1
         sta     APPMHI+1
 
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
 
 ; Atari XL target stuff...
 
@@ -224,7 +224,7 @@ _exit:  jsr     donelib         ; Run module destructors
 spsave:         .res    1
 old_shflok:     .res    1
 old_lmargin:    .res    1
-.if .not .defined(__ATARIXL__)
+.ifndef __ATARIXL__
 APPMHI_save:    .res    2
 .endif
 
diff --git a/libsrc/atari/irq.s b/libsrc/atari/irq.s
index 597ad9d60..3fbdc971b 100644
--- a/libsrc/atari/irq.s
+++ b/libsrc/atari/irq.s
@@ -39,7 +39,7 @@ doneirq:
 
 IRQStub:
         cld                             ; Just to be sure
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
 	pha
 	lda	PORTB
 	pha
@@ -47,7 +47,7 @@ IRQStub:
 	sta	PORTB			; disable ROM  @@@ TODO: update CHARGEN
 .endif
         jsr     callirq                 ; Call the functions
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
 	pla
 	sta	PORTB
 	pla
diff --git a/libsrc/atari/libref.s b/libsrc/atari/libref.s
index 6d93a0b8e..171bd6de6 100644
--- a/libsrc/atari/libref.s
+++ b/libsrc/atari/libref.s
@@ -7,7 +7,7 @@
 
 em_libref       := _exit
 joy_libref      := _exit
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
         .import CIO_handler
 tgi_libref      := CIO_handler
 .else
diff --git a/libsrc/atari/ostype.s b/libsrc/atari/ostype.s
index 7a3342d2a..4fbeaaf70 100644
--- a/libsrc/atari/ostype.s
+++ b/libsrc/atari/ostype.s
@@ -40,7 +40,7 @@
 
         .export         _get_ostype
 
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
 
         .include "atari.inc"
         .import __CHARGEN_START__
diff --git a/libsrc/atari/save_area.s b/libsrc/atari/save_area.s
index 2fddce017..5495be8ca 100644
--- a/libsrc/atari/save_area.s
+++ b/libsrc/atari/save_area.s
@@ -6,7 +6,7 @@
 ; Christian Groessler, chris@groessler.org, 2013
 ;
 
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
 
 .export		SAVMSC_save
 .export		MEMTOP_save
diff --git a/libsrc/atari/shadow_ram_handlers.s b/libsrc/atari/shadow_ram_handlers.s
index c01f56ddb..9714644ad 100644
--- a/libsrc/atari/shadow_ram_handlers.s
+++ b/libsrc/atari/shadow_ram_handlers.s
@@ -8,7 +8,7 @@ DEBUG	=	1
 USEWSYNC=	1
 CHKBUF	=	1	; check if bounce buffering is needed (bounce buffering is always done if set to 0)
 
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
 
 	SHRAM_HANDLERS	= 1
         .include        "atari.inc"
@@ -1147,4 +1147,4 @@ orig_len:		.res	2
 req_len:		.res	2
 retlen:			.res	2
 
-.endif	; .if .defined(__ATARIXL__)
+.endif	; .ifdef __ATARIXL__
diff --git a/libsrc/atari/shadow_ram_prepare.s b/libsrc/atari/shadow_ram_prepare.s
index 4dd0338b9..be40baed3 100644
--- a/libsrc/atari/shadow_ram_prepare.s
+++ b/libsrc/atari/shadow_ram_prepare.s
@@ -11,7 +11,7 @@
 
 DEBUG   =       1
 
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
 
         .export         sramprep
         .import         __SRPREP_LOAD__, __SRPREPCHNK_LAST__
@@ -403,4 +403,4 @@ screen_device_length = * - screen_device
         .word   INITAD+1
         .word   sramprep
 
-.endif  ; .if .defined(__ATARIXL__)
+.endif  ; .ifdef __ATARIXL__
diff --git a/libsrc/atari/system_check.s b/libsrc/atari/system_check.s
index b1d80b0c2..b01311a4b 100644
--- a/libsrc/atari/system_check.s
+++ b/libsrc/atari/system_check.s
@@ -13,7 +13,7 @@
 
 DEBUG	=	1
 
-.if .defined(__ATARIXL__)
+.ifdef __ATARIXL__
 
 	.export		syschk
         .import         __SYSCHK_LOAD__
@@ -154,4 +154,4 @@ end:
         .word   INITAD+1
         .word   syschk
 
-.endif	; .if .defined(__ATARIXL__)
+.endif	; .ifdef __ATARIXL__