diff --git a/src/racket/src/jit.h b/src/racket/src/jit.h
index c00faec873..a0dcee60a5 100644
--- a/src/racket/src/jit.h
+++ b/src/racket/src/jit.h
@@ -799,7 +799,7 @@ void scheme_jit_prolog_again(mz_jit_state *jitter, int n, int ret_addr_reg)
 # ifdef JIT_X86_64
 #  define mz_pop_threadlocal() mz_get_local_p(JIT_R14, JIT_LOCAL4)
 #  define mz_push_threadlocal(in) /* empty */
-#  define mz_push_threadlocal_early() (mz_set_local_p(JIT_R14, JIT_LOCAL4), jit_movr_p(JIT_R14, JIT_R1))
+#  define mz_push_threadlocal_early() (mz_set_local_p(JIT_R14, JIT_LOCAL4), jit_movr_p(JIT_R14, JIT_R_ARG4))
 #  define mz_repush_threadlocal() mz_set_local_p(JIT_R14, JIT_LOCAL4)
 # else
 #  define mz_pop_threadlocal() /* empty */
diff --git a/src/racket/src/lightning/i386/core.h b/src/racket/src/lightning/i386/core.h
index 1d1adbca37..7de9cd21ef 100644
--- a/src/racket/src/lightning/i386/core.h
+++ b/src/racket/src/lightning/i386/core.h
@@ -368,11 +368,13 @@ struct jit_local_state {
 #  define jit_getprearg_pip_p(r) (MOVQrr(JIT_R(9), r))
 #  define jit_getprearg_pipp_p(r) (jit_ldxi_p(r, JIT_SP, 40))
 #  define jit_getprearg_pippp_p(r) (jit_ldxi_p(r, JIT_SP, 48))
+#  define JIT_R_ARG4 JIT_R(9)
 # else
 #  define jit_getprearg__p(r) (MOVQrr(_EDI, r))
 #  define jit_getprearg_pip_p(r) (MOVQrr(_ECX, r))
 #  define jit_getprearg_pipp_p(r) (MOVQrr(JIT_R(8), r))
 #  define jit_getprearg_pippp_p(r) (MOVQrr(JIT_R(9), r))
+#  define JIT_R_ARG4 _ECX
 # endif
 #else
 # define jit_getprearg__p(r) (jit_ldxi_p(r, JIT_SP, 4))
diff --git a/src/worksp/gc2/XFORM-LOCK b/src/worksp/gc2/XFORM-LOCK
new file mode 100644
index 0000000000..e69de29bb2