diff --git a/contrib/kiss-chroot b/contrib/kiss-chroot
index b1db149..fef7fbe 100755
--- a/contrib/kiss-chroot
+++ b/contrib/kiss-chroot
@@ -64,8 +64,8 @@ log Entering chroot; {
         SHELL=/bin/sh \
         USER=root \
         KISS_ASROOT=1 \
-        CFLAGS="${2:--march=x86-64 -mtune=generic -pipe -Os}" \
-        CXXFLAGS="${2:--march=x86-64 -mtune=generic -pipe -Os}" \
-        MAKEFLAGS="-j$(nproc 2>/dev/null || echo 1)" \
+        CFLAGS="${CFLAGS:--march=x86-64 -mtune=generic -pipe -Os}" \
+        CXXFLAGS="${CXXFLAGS:--march=x86-64 -mtune=generic -pipe -Os}" \
+        MAKEFLAGS="${MAKEFLAGS:--j$(nproc 2>/dev/null || echo 1)}" \
         /bin/sh -l
 }