diff --git a/rootfs.py b/rootfs.py
index cb40332..9100f1e 100755
--- a/rootfs.py
+++ b/rootfs.py
@@ -39,6 +39,7 @@ def create_configuration_file(args):
             config.write("KERNEL_BOOTSTRAP=True\n")
         else:
             config.write("KERNEL_BOOTSTRAP=False\n")
+        config.write(f"BUILD_KERNELS={args.build_kernels}\n")
 
 # pylint: disable=too-many-statements
 def main():
@@ -73,6 +74,9 @@ def main():
     parser.add_argument("--external-sources",
                         help="Download sources externally from live-bootstrap.",
                         action="store_true")
+    parser.add_argument("--build-kernels",
+                        help="Also build kernels in chroot and bwrap builds.",
+                        action="store_true")
     parser.add_argument("--no-create-config",
                         help="Do not automatically create config file",
                         action="store_true")
diff --git a/sysa/run.kaem b/sysa/run.kaem
index eb5e7bb..f17c69b 100755
--- a/sysa/run.kaem
+++ b/sysa/run.kaem
@@ -45,7 +45,17 @@ cd ${pkg}
 kaem --file ${pkg}.kaem
 cd ..
 
+BUILD_FIWIX=False
+
 if match x${KERNEL_BOOTSTRAP} xTrue; then
+    BUILD_FIWIX=True
+fi
+
+if match x${BUILD_KERNELS} xTrue; then
+    BUILD_FIWIX=True
+fi
+
+if match x${BUILD_FIWIX} xTrue; then
     # The Fiwix kernel
     pkg="fiwix-1.4.0-lb1"
     cd ${pkg}
@@ -58,14 +68,16 @@ if match x${KERNEL_BOOTSTRAP} xTrue; then
     kaem --verbose --file ${pkg}.kaem
     cd ..
 
-    # Build the ext2 image
-    make_fiwix_initrd
-
     # Live boot loader for Fiwix
     pkg="kexec-fiwix"
     cd ${pkg}
     kaem --verbose --file ${pkg}.kaem
     cd ..
+fi
+
+if match x${KERNEL_BOOTSTRAP} xTrue; then
+    # Build the ext2 image
+    make_fiwix_initrd
 
     # Boot Fiwix
     kexec-fiwix
diff --git a/sysa/run2.sh b/sysa/run2.sh
index 7c46c01..53a28e3 100755
--- a/sysa/run2.sh
+++ b/sysa/run2.sh
@@ -73,7 +73,7 @@ build ed-1.4
 
 build bc-1.07.1
 
-if [ "${CHROOT}" = False ]; then
+if [ "${CHROOT}" = False ] || [ "${BUILD_KERNELS}" = True ]; then
     # Save because linux deletes all distfiles to save space
     cp "${DISTFILES}"/musl-1.2.3.tar.gz "${SOURCES}"/musl-1.2.3
 fi
@@ -86,13 +86,15 @@ grep --no-filename '^build' "${SOURCES}"/run*.sh | grep -v musl-1.2.3 | sed "s/b
     rm -rf "${SOURCES:?}/${p:?}"
 done
 
-if [ "${CHROOT}" = False ]; then
+if [ "${CHROOT}" = False ] || [ "${BUILD_KERNELS}" = True ]; then
     build kexec-tools-2.0.22
 
     build linux-4.9.10
+fi
 
-    build musl-1.2.3 '' no-patches
+build musl-1.2.3 '' no-patches
 
+if [ "${CHROOT}" = False ]; then
     create_sysb
     if [ "${KERNEL_BOOTSTRAP}" = True ]; then
         echo "Kernel bootstrapping successful."
@@ -101,8 +103,6 @@ if [ "${CHROOT}" = False ]; then
         go_sysb
     fi
 else
-    build musl-1.2.3 '' no-patches
-
     # In chroot mode transition directly into System C.
     SYSC=/sysc_image
     sys_transfer "${SYSC}" /sysc gzip patch