Since the last merge from upstream (jdk-26+26), the UnsafeIntrinsicsTest fails with ZGC:

#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/home/bits/go/src/github.com/openjdk/lilliput/src/hotspot/share/gc/z/zAddress.inline.hpp:452), pid=4088734, tid=4088738
# assert(!assert_on_failure) failed: Missing heap base: 0x00007080dcc08208
#
# JRE version: OpenJDK Runtime Environment (26.0) (fastdebug build 26-internal-adhoc.bits.lilliput)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 26-internal-adhoc.bits.lilliput, mixed mode, sharing, tiered, compact obj headers, z gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0x1e6e0c3] check_is_valid_zaddress(oopDesc*)+0xc3
#

Can be reproduced only with fastdebug build. Slowdebug curiously passes.
make test TEST=compiler/gcbarriers/UnsafeIntrinsicsTest.java TEST_VM_OPTS="-XX:+UseCompactObjectHeaders"

Full hs_err attached.