diff --git a/bootfiles/18c/boot4.lisp b/bootfiles/18c/boot4.lisp
new file mode 100644
index 0000000000000000000000000000000000000000..f4d06c4d84dbacf8385239fca17c29277cf4e2e9
--- /dev/null
+++ b/bootfiles/18c/boot4.lisp
@@ -0,0 +1,14 @@
+(in-package "VM")
+
+;; Add some new constants for the Sparc backend.
+#+sparc
+(progn
+  (defconstant fixnum-tag-bits (1- lowtag-bits)
+    "Number of tag bits used for a fixnum")
+
+  (defconstant fixnum-tag-mask (1- (ash 1 fixnum-tag-bits))
+    "Mask to get the fixnum tag")
+
+  (defconstant positive-fixnum-bits (- word-bits fixnum-tag-bits 1)
+    "Maximum number of bits in a positive fixnum")
+  )
diff --git a/bootfiles/18c/sparc-boot1.lisp b/bootfiles/18c/sparc-boot1.lisp
deleted file mode 100644
index 699818088d2035be613026cd86fb9fe10bea2f67..0000000000000000000000000000000000000000
--- a/bootfiles/18c/sparc-boot1.lisp
+++ /dev/null
@@ -1,9 +0,0 @@
-(in-package "VM")
-(defconstant fixnum-tag-bits (1- lowtag-bits)
-  "Number of tag bits used for a fixnum")
-
-(defconstant fixnum-tag-mask (1- (ash 1 fixnum-tag-bits))
-  "Mask to get the fixnum tag")
-
-(defconstant positive-fixnum-bits (- word-bits fixnum-tag-bits 1)
-  "Maximum number of bits in a positive fixnum")