diff --git a/mach/m68k2/libsys/brk.s b/mach/m68k2/libsys/brk.s
index f337c0533..0d33d0739 100644
--- a/mach/m68k2/libsys/brk.s
+++ b/mach/m68k2/libsys/brk.s
@@ -3,14 +3,15 @@
 .extern _brk
 .extern _sbrk
 .text
-_sbrk:		move.l nd,d0
-		add.l  d0, 4(sp)
+_sbrk:		move.l nd,a0
+		add.w  4(sp),a0
 		move.w #0x11,d0
-		move.l 4(sp),a0
 		trap #0
 		bcs lcerror
 		move.l nd,d0
-		move.l 4(sp),nd
+		move.l d0,a0
+		add.w  4(sp),a0
+		move.l a0,nd
 		rts
 lcerror:	jmp cerror
 _brk:		move.w #0x11,d0
diff --git a/mach/m68k4/libsys/brk.s b/mach/m68k4/libsys/brk.s
index f337c0533..0d33d0739 100644
--- a/mach/m68k4/libsys/brk.s
+++ b/mach/m68k4/libsys/brk.s
@@ -3,14 +3,15 @@
 .extern _brk
 .extern _sbrk
 .text
-_sbrk:		move.l nd,d0
-		add.l  d0, 4(sp)
+_sbrk:		move.l nd,a0
+		add.w  4(sp),a0
 		move.w #0x11,d0
-		move.l 4(sp),a0
 		trap #0
 		bcs lcerror
 		move.l nd,d0
-		move.l 4(sp),nd
+		move.l d0,a0
+		add.w  4(sp),a0
+		move.l a0,nd
 		rts
 lcerror:	jmp cerror
 _brk:		move.w #0x11,d0