diff --git a/CHANGELOG.rdoc b/CHANGELOG.rdoc
index 472e5a7b5c1..c9ac86975f5 100644
--- a/CHANGELOG.rdoc
+++ b/CHANGELOG.rdoc
@@ -2,6 +2,7 @@
 
 ==== Bug fixes
 
+* Fix a bug where CFLAGS passed in are dropped.
 * Fix a bug where CSS selector :nth(n) did not work (#1187).
 
 === 1.6.4 / 2014-11-04
diff --git a/ext/nokogiri/extconf.rb b/ext/nokogiri/extconf.rb
index ce2e19b3549..a71f63dbb70 100644
--- a/ext/nokogiri/extconf.rb
+++ b/ext/nokogiri/extconf.rb
@@ -452,6 +452,10 @@ def install
     end
   end
 
+  preserving_globals {
+    have_library('z', 'gzdopen', 'zlib.h')
+  } or abort 'zlib is missing; necessary for building libxml2'
+
   libxml2_recipe = process_recipe("libxml2", dependencies["libxml2"], static_p, cross_build_p) do |recipe|
     recipe.files = ["ftp://ftp.xmlsoft.org/libxml2/#{recipe.name}-#{recipe.version}.tar.gz"]
     recipe.configure_options += [