diff -Nru happy-1.19.5/debian/changelog happy-1.19.5/debian/changelog
--- happy-1.19.5/debian/changelog	2015-12-03 20:16:46.000000000 +0000
+++ happy-1.19.5/debian/changelog	2015-12-22 02:39:05.000000000 +0000
@@ -1,3 +1,9 @@
+happy (1.19.5-5) unstable; urgency=medium
+
+  * Implement a stage1 profile build for bootstrapping.
+
+ -- Colin Watson <cjwatson@debian.org>  Tue, 22 Dec 2015 02:39:03 +0000
+
 happy (1.19.5-4) unstable; urgency=medium
 
   * Switch Vcs-Git/Vcs-Browser headers to new location.
diff -Nru happy-1.19.5/debian/control happy-1.19.5/debian/control
--- happy-1.19.5/debian/control	2015-12-03 19:18:03.000000000 +0000
+++ happy-1.19.5/debian/control	2015-12-22 02:36:21.000000000 +0000
@@ -6,7 +6,8 @@
 Standards-Version: 3.9.6
 Build-Depends: cdbs (>= 0.4.59),
                haskell-devscripts (>= 0.10),
-               debhelper (>= 9),
+               debhelper (>= 9.20141010),
+               dpkg-dev (>= 1.17.14),
                autoconf,
                docbook-utils,
                ghc (>= 7.10),
@@ -14,7 +15,7 @@
                docbook-xml,
                xsltproc,
                libghc-mtl-dev,
-               happy
+               happy <!stage1>
 Homepage: http://www.haskell.org/happy
 Vcs-Git: git://git.debian.org/git/pkg-haskell/DHG_packages.git
 Vcs-Browser: https://anonscm.debian.org/cgit/pkg-haskell/DHG_packages.git/
diff -Nru happy-1.19.5/debian/rules happy-1.19.5/debian/rules
--- happy-1.19.5/debian/rules	2015-07-16 00:45:52.000000000 +0000
+++ happy-1.19.5/debian/rules	2015-12-22 02:36:21.000000000 +0000
@@ -13,6 +13,13 @@
 include /usr/share/cdbs/1/class/hlibrary.mk
 include /usr/share/cdbs/1/rules/utils.mk
 
+ifneq (,$(filter stage1,$(DEB_BUILD_PROFILES)))
+DEB_SETUP_GHC_CONFIGURE_ARGS += --with-happy=/bin/true
+
+cleanbuilddir/happy::
+	cp -a dist/build/happy/happy-tmp/*.hs src/
+endif
+
 clean::
 	[ ! -f doc/config.mk ] || $(MAKE) -C doc clean