diff --git a/scripts/xz_wrap.sh b/scripts/xz_wrap.sh
index bb760b721b2c..c8c36441ab70 100755
--- a/scripts/xz_wrap.sh
+++ b/scripts/xz_wrap.sh
@@ -16,4 +16,15 @@ case $SRCARCH in
 	sparc)          BCJ=--sparc ;;
 esac
 
-exec $XZ --check=crc32 $BCJ --lzma2=$LZMA2OPTS,dict=32MiB
+# Use single-threaded mode because it compresses a little better
+# (and uses less RAM) than multithreaded mode.
+#
+# For the best compression, the dictionary size shouldn't be
+# smaller than the uncompressed kernel. 128 MiB dictionary
+# needs less than 1400 MiB of RAM in single-threaded mode.
+#
+# On the archs that use this script to compress the kernel,
+# decompression in the preboot code is done in single-call mode.
+# Thus the dictionary size doesn't affect the memory requirements
+# of the preboot decompressor at all.
+exec $XZ --check=crc32 --threads=1 $BCJ --lzma2=$LZMA2OPTS,dict=128MiB