diff --git a/libsrc/common/_printf.h b/libsrc/common/_printf.h
index 03e8f7307..9b5c26609 100644
--- a/libsrc/common/_printf.h
+++ b/libsrc/common/_printf.h
@@ -34,7 +34,7 @@ struct outdesc {
 
 
 /* Internal formatting routine */
-int _printf (struct outdesc* d, const char* format, va_list ap);
+int __fastcall__ _printf (struct outdesc* d, const char* format, va_list ap);
 
 
 
diff --git a/libsrc/common/_printf.s b/libsrc/common/_printf.s
index d60ebdfe9..f390828ae 100644
--- a/libsrc/common/_printf.s
+++ b/libsrc/common/_printf.s
@@ -241,16 +241,17 @@ __printf:
 
 ; Save the register bank variables into the save area
 
-	ldx	#5
-Save:	lda	regbank,x
-     	sta	RegSave,x
-     	dex
+ 	pha				; Save low byte of ap
+       	ldy	#5
+Save:	lda	regbank,y
+     	sta	RegSave,y
+     	dey
        	bpl	Save
 
 ; Get the parameters from the stack
 
-	jsr	popax	       		; Argument list pointer
-	sta	ArgList
+	pla				; Restore low byte of ap
+	sta	ArgList			; Argument list pointer
 	stx	ArgList+1
 
 	jsr	popax	       		; Format string
diff --git a/libsrc/common/printf.s b/libsrc/common/printf.s
index ad26b8655..3f95f8e6b 100644
--- a/libsrc/common/printf.s
+++ b/libsrc/common/printf.s
@@ -60,15 +60,15 @@ _printf:
 	lda	(ptr1),y
 	jsr	pushax
 
-; Push the va_list
+; Push va_list (last parameter to vfprintf)
 
-	lda	ptr1
-	ldx	ptr1+1
+	lda    	ptr1
+	ldx    	ptr1+1
 	jsr	pushax
 
 ; Call vfprintf
 
-	jsr	_vfprintf	
+	jsr	_vfprintf
 
 ; Cleanup the stack. We will return what we got from vfprintf