diff --git a/bootfiles/18d/boot3.lisp b/bootfiles/18d/boot3.lisp
new file mode 100644
index 0000000000000000000000000000000000000000..8b0b50fdcd5c2f046fdf8039b946b607374391b2
--- /dev/null
+++ b/bootfiles/18d/boot3.lisp
@@ -0,0 +1,7 @@
+;; Unexport the newly re-introduced compiler-macroexpand* symbols from
+;; the CL package.  This is for the benefit of old cores, which might
+;; still have those "exported", even though the functions (or even the
+;; symbols) don't exist.  This is deep CMUCL voodoo magic, don't even
+;; try to understand it.
+
+(unexport '(CL::COMPILER-MACROEXPAND-1 CL::COMPILER-MACROEXPAND) "CL")