diff --git a/.githooks/update b/.githooks/update
new file mode 100755
index 00000000..2a0dbca1
--- /dev/null
+++ b/.githooks/update
@@ -0,0 +1,10 @@
+#!/bin/sh
+
+old="$2"
+new="$3"
+
+# fail if we add any new lines to C or Scheme source containing a tab
+git diff --name-only "$old" "$new" |\
+    egrep '\.(cpp|h|scm|sld|stub)$' |\
+    xargs -d'\n' git diff -U0 "$old" "$new" -- |\
+    grep -q $'^+.*\t' && exit 1
diff --git a/Makefile b/Makefile
index be2412ba..da5a563a 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 # -*- makefile-gmake -*-
 
-.PHONY: dist mips-dist cleaner test test-all test-dist checkdefs debian snowballs
+.PHONY: dist mips-dist cleaner test test-all test-dist checkdefs debian snowballs init-dev
 .DEFAULT_GOAL := all
 
 CHIBI_VERSION ?= $(shell cat VERSION)
@@ -69,6 +69,10 @@ include Makefile.libs
 
 all: chibi-scheme$(EXE) all-libs chibi-scheme.pc $(META_FILES)
 
+# Please run this if you want to contribute.
+init-dev:
+	git config core.hooksPath .githooks
+
 js: js/chibi.js
 
 js/chibi.js: chibi-scheme-emscripten chibi-scheme-static.bc js/pre.js js/post.js js/exported_functions.json