diff --git a/changelog b/changelog
new file mode 100644
--- /dev/null
+++ b/changelog
@@ -0,0 +1,6 @@
+tip-lib 0.1.1 (released 2015-06-11):
+* List alex and happy as build-tools (thanks to Peter Simons.)
+* Add errors.h as extra source file.
+
+tip-lib 0.1 (released 2015-06-11):
+* Initial release.
diff --git a/src/errors.h b/src/errors.h
new file mode 100644
--- /dev/null
+++ b/src/errors.h
@@ -0,0 +1,4 @@
+-- Inspired by Agda's undefined.h
+#define __ ERROR("no error message given")
+#define ERROR(msg) (error (__FILE__ ++ ", line " ++ show (__LINE__ :: Int) ++ ": " ++ msg))
+#define FROMJUST(msg) (\ m -> case m of { Just x -> x; Nothing -> ERROR(msg) })
diff --git a/tip-lib.cabal b/tip-lib.cabal
--- a/tip-lib.cabal
+++ b/tip-lib.cabal
@@ -1,5 +1,5 @@
 name:                tip-lib
-version:             0.1
+version:             0.1.1
 synopsis:            tons of inductive problems - support library and tools
 description:         This package provides a tool for processing inductive theorem proving problems in TIP format (see the homepage for details).
 homepage:            http://tip-org.github.io
@@ -12,9 +12,12 @@
 build-type:          Simple
 cabal-version:       >=1.10
 
+extra-source-files:  changelog src/errors.h
+
 source-repository head
   type:     git
   location: http://github.com/tip-org/tools
+  subdir:   tip-lib
 
 library
   exposed-modules:
@@ -77,6 +80,7 @@
                        pretty,
                        array,
                        optparse-applicative
+  build-tools:         alex, happy
 
 executable tip
   main-is:             executable/Main.hs