diff --git a/core/cpu/ppc/bootstrap.factor b/core/cpu/ppc/bootstrap.factor
index c57a97aed5..d8644e24a6 100644
--- a/core/cpu/ppc/bootstrap.factor
+++ b/core/cpu/ppc/bootstrap.factor
@@ -24,8 +24,8 @@ big-endian on
 
 : next-save stack-frame bootstrap-cell - ;
 : xt-save stack-frame 2 bootstrap-cells - ;
-: scan-save stack-frame 3 bootstrap-cells - ;
-: array-save stack-frame 4 bootstrap-cells - ;
+: array-save stack-frame 3 bootstrap-cells - ;
+: scan-save stack-frame 4 bootstrap-cells - ;
 
 [
     temp-reg quot-reg quot-array@ LWZ          ! load array
diff --git a/vm/callstack.c b/vm/callstack.c
index 4ac2457dea..62ea3f9040 100644
--- a/vm/callstack.c
+++ b/vm/callstack.c
@@ -65,7 +65,6 @@ DEFINE_PRIMITIVE(callstack)
 		size = 0;
 
 	F_CALLSTACK *callstack = allot_callstack(size);
-	callstack->bottom = (CELL)bottom;
 	memcpy(FIRST_STACK_FRAME(callstack),top,size);
 	dpush(tag_object(callstack));
 }
diff --git a/vm/callstack.h b/vm/callstack.h
index 6bbebfcd34..4d1dac9ffd 100644
--- a/vm/callstack.h
+++ b/vm/callstack.h
@@ -1,21 +1,3 @@
-typedef struct _F_STACK_FRAME
-{
-	/* In compiled quotation frames, position within the array.
-	In compiled word frames, unused. */
-	CELL scan;
-
-	/* In compiled quotation frames, the quot->array slot.
-	In compiled word frames, unused. */
-	CELL array;
-
-	/* In all compiled frames, the XT on entry. */
-	XT xt;
-
-	/* Pointer to the next stack frame; frames are chained from
-	the bottom on up */
-	struct _F_STACK_FRAME *next;
-} F_STACK_FRAME;
-
 F_FASTCALL void save_callstack_bottom(F_STACK_FRAME *callstack_bottom);
 
 #define FIRST_STACK_FRAME(stack) (F_STACK_FRAME *)((stack) + 1)
diff --git a/vm/layouts.h b/vm/layouts.h
index fc59802f36..cd1c242303 100644
--- a/vm/layouts.h
+++ b/vm/layouts.h
@@ -238,6 +238,21 @@ typedef struct {
 	CELL header;
 	/* tagged */
 	CELL length;
-	/* untagged */
-	CELL bottom;
 } F_CALLSTACK;
+
+typedef struct
+{
+	/* In compiled quotation frames, position within the array.
+	In compiled word frames, unused. */
+	CELL scan;
+
+	/* In compiled quotation frames, the quot->array slot.
+	In compiled word frames, unused. */
+	CELL array;
+
+	/* In all compiled frames, the XT on entry. */
+	XT xt;
+
+	/* Frame size in bytes */
+	CELL size;
+} F_STACK_FRAME;