diff --git a/java-25-openjdk.spec b/java-25-openjdk.spec
index ebc92dd..c6f5262 100644
--- a/java-25-openjdk.spec
+++ b/java-25-openjdk.spec
@@ -1,5 +1,5 @@
 # debug_package %%{nil} is portable-jdks specific
-%define  debug_package %{nil}
+%define debug_package %{nil}
 
 # RPM conditionals so as to be able to dynamically produce
 # slowdebug/release builds. See:
@@ -335,7 +335,7 @@
 # buildjdkver is usually same as %%{featurever},
 # but in time of bootstrap of next jdk, it is featurever-1,
 # and this it is better to change it here, on single place
-%global buildjdkver %(expr %{featurever} - 1)
+%global buildjdkver %{featurever}
 # We don't add any LTS designator for STS packages (Fedora and EPEL).
 # We need to explicitly exclude EPEL as it would have the %%{rhel} macro defined.
 %if 0%{?rhel} && !0%{?epel}
@@ -346,8 +346,12 @@
   %global lts_designator_zip ""
 %endif
 # JDK to use for bootstrapping
-%global bootjdkpkg java-21-openjdk
-%global bootjdk /usr/lib/jvm/%{bootjdkpkg}
+%global bootjdkpkg java-%{fakefeaturever}-openjdk
+%ifarch %{fastdebug_arches}
+%global bootdebugpkg fastdebug
+%endif
+%global bootjdkzip %{_jvmdir}/%{bootjdkpkg}-*.portable%{?bootdebugpkg:.%{bootdebugpkg}}.jdk.%{_arch}.tar.xz
+%global bootjdk %{_builddir}/%{bootjdkpkg}.boot
 # Define whether to use the bootstrap JDK directly or with a fresh libjvm.so
 # This will only work where the bootstrap JDK is the same major version
 # as the JDK being built
@@ -397,7 +401,7 @@
 %global top_level_dir_name   %{vcstag}
 %global top_level_dir_name_backup %{top_level_dir_name}-backup
 %global buildver        9
-%global rpmrelease      1
+%global rpmrelease      2
 #%%global tagsuffix     %%{nil}
 # Priority must be 8 digits in total; up to openjdk 1.8, we were using 18..... so when we moved to 11, we had to add another digit
 %if %is_system_jdk
@@ -734,7 +738,7 @@ BuildRequires: zip
 BuildRequires: tar
 BuildRequires: unzip
 BuildRequires: javapackages-filesystem
-BuildRequires: %{bootjdkpkg}%{?pkgos:-%{pkgos}}-devel
+BuildRequires: %{bootjdkpkg}-portable-devel%{?bootdebugpkg:-%{bootdebugpkg}}
 # Zero-assembler build requirement
 %ifarch %{zero_arches}
 BuildRequires: libffi-devel
@@ -1057,6 +1061,16 @@ done
 %endif
 %endif
 
+# Extract build JDK
+pushd %{_jvmdir}
+sha256sum --check %{bootjdkzip}.sha256sum
+popd
+tar -xJf %{bootjdkzip}
+mv java-%{fakefeaturever}-openjdk-%{featurever}* %{bootjdk}
+# Print release information
+echo "Installed boot JDK:"
+cat %{bootjdk}/release
+
 %build
 # How many CPU's do we have?
 export NUM_PROC=%(/usr/bin/getconf _NPROCESSORS_ONLN 2> /dev/null || :)
@@ -1629,7 +1643,7 @@ done # end of release / debug cycle loop
 # We test debug first as it will give better diagnostics on a crash
 for suffix in %{build_loop} ; do
 
-# portable builds have static_libs embedded, thus top_dir_abs_main_build_path is same as  top_dir_abs_staticlibs_build_path
+# portable builds have static_libs embedded, thus top_dir_abs_main_build_path is same as top_dir_abs_staticlibs_build_path
 top_dir_abs_main_build_path=$(pwd)/%{installoutputdir -- ${suffix}}
 %if %{include_staticlibs}
 top_dir_abs_staticlibs_build_path=${top_dir_abs_main_build_path}
@@ -1943,6 +1957,12 @@ done
 %endif
 
 %changelog
+* Mon Sep 22 2025 Andrew Hughes <gnu.andrew@redhat.com> - 1:22.0.2.0.9-2
+- Build using ourselves rather than the system JDK as java-25-openjdk is unavailable on older systems
+- Switch buildjdkver back to featurever temporarily for this rebuild
+- Introduce bootjdkpkg to handle architectures not in fastdebug_arches (i.e. s390x)
+- Related: RHELBU-3203
+
 * Sat Sep 20 2025 Andrew Hughes <gnu.andrew@redhat.com> - 1:22.0.2.0.9-1
 - Update to jdk-22.0.2+9 (GA)
 - Update release notes with features of JDK 22