diff --git a/.circleci/config.yml b/.circleci/config.yml
index 9ed12cff..1113d536 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -2,7 +2,7 @@ version: 2
 jobs:
   build:
     macos:
-      xcode: "11.3.1"
+      xcode: "12.5.1"
     environment:
       # OPAM seems to be quite unhappy without $TERM and Circle doesn't seem to set one.
       TERM: vt100
diff --git a/test/tinycore.sh b/test/tinycore.sh
index 3e2f65c0..9a5843b5 100755
--- a/test/tinycore.sh
+++ b/test/tinycore.sh
@@ -1,6 +1,10 @@
-#!/bin/sh
+#!/bin/sh -x
 set -e
 
+# debug
+sysctl machdep.cpu
+#ioreg -l
+
 # These are binaries from a mirror of
 #  http://tinycorelinux.net
 # with the following patch applied: