diff --git a/kernel.spec b/kernel.spec
index becbcf3..f2e9d7b 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -11,7 +11,7 @@
 %define sublevel	6
 
 # Release number. Increase this before a rebuild.
-%define rpmrel		1
+%define rpmrel		3
 %define fullrpmrel	%{rpmrel}
 
 %define rpmtag		%{disttag}
@@ -966,6 +966,17 @@ cp arch/x86/configs/%{arch_suffix}_defconfig-%{flavour} .config
 # make sure EXTRAVERSION says what we want it to say
 LC_ALL=C sed -ri "s/^EXTRAVERSION.*/EXTRAVERSION = -%{flavour}-%{buildrpmrel}/" Makefile
 
+# Print debug messages when loglevel=7 in cmdline.
+# Those messages can be caught by debugfs without -DDEBUG.
+# but sometimes it is required to see them via a serial port when booting the kernel.
+# '#ifdef DEBUG' is used in different places for different purposes,
+# so change DEBUG to PRINTK_DEBUG in one specific place.
+%if %build_debug
+sed -i %{src_dir}/include/linux/printk.h \
+	-e 's,^#ifdef DEBUG$,#if defined(DEBUG) || defined(PRINTK_DEBUG),g'
+export KCPPFLAGS="-DPRINTK_DEBUG"
+%endif
+
 # build the kernel
 echo "Building kernel %{kver_full}"