diff --git a/doc/install.html b/doc/install.html
index 2b47eb514a..843e0645fe 100644
--- a/doc/install.html
+++ b/doc/install.html
@@ -91,7 +91,9 @@ installed as part of
 <a href="http://developer.apple.com/TOOLS/Xcode/">Xcode</a>. 
 </p>
 
-<p>On Ubuntu/Debian, use <code>sudo apt-get install bison ed gawk gcc libc6-dev make</code>.
+<p>On Ubuntu/Debian, use <code>sudo apt-get install bison ed gawk gcc libc6-dev
+make</code>. If you want to build 32-bit binaries on a 64-bit system you'll
+also need the <code>libc6-dev-i386</code> package.
 </p>
 
 <h2 id="mercurial">Install Mercurial, if needed</h2>