diff --git a/ext/libxml/extconf.rb b/ext/libxml/extconf.rb
index 21c802ac..91a9238d 100644
--- a/ext/libxml/extconf.rb
+++ b/ext/libxml/extconf.rb
@@ -63,5 +63,10 @@ def crash(str)
     EOL
 end
 
+# Optional zlib support via libxml2; defines HAVE_ZLIB_H if available.
+unless have_header("zlib.h")
+  message "zlib not found: building without compression support\n"
+end
+
 create_header()
 create_makefile('libxml_ruby')