diff --git a/pkgs/development/libraries/avahi/common.nix b/pkgs/development/libraries/avahi/common.nix
index 1ebadc26e268..6b9c726f100c 100644
--- a/pkgs/development/libraries/avahi/common.nix
+++ b/pkgs/development/libraries/avahi/common.nix
@@ -1,5 +1,7 @@
 sha256: args: with args;
 
+assert qt4Support -> qt4 != null;
+
 stdenv.mkDerivation rec {
   name = "avahi-" + version;
   src = fetchurl {
@@ -7,12 +9,21 @@ stdenv.mkDerivation rec {
     inherit sha256;
   };
 
-  buildInputs = [pkgconfig libdaemon dbus perl perlXMLParser glib qt4];
+  buildInputs = [pkgconfig libdaemon dbus perl perlXMLParser glib expat]
+    ++ lib.optional qt4Support qt4;
 
-  configureFlags = "--disable-qt3 --disable-gdbm --disable-gtk --disable-mono
-    --with-distro=none --enable-shared --disable-static --disable-python";
+  configureFlags = ''
+    --disable-qt3 --disable-gdbm --disable-gtk --disable-mono
+    --${if qt4Support then "enable" else "disable"}-qt4
+    --with-distro=none --enable-shared --disable-static --disable-python
+  '';
 
   meta = {
+    description = ''Avahi is a system which facilitates service discovery
+                    on a local network.  It is an implementation of the
+		    mDNS (for "Multicast DNS") and DNS-SD (for "DNS-Based
+		    Service Discovery") protocols.'';
     homepage = http://avahi.org;
+    license = "LGPLv2+";
   };
 }
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 3c7e4415a61b..d775aacc101b 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -386,11 +386,19 @@ rec {
     inherit fetchurl stdenv zlib wxGTK;
   };
 
-  avahi = selectVersion ../development/libraries/avahi "0.6.22" {
-    inherit stdenv fetchurl pkgconfig libdaemon dbus perl perlXMLParser qt4
-      python expat;
-    inherit (gtkLibs) glib gtk;
-  };
+  avahi =
+    # XXX: Versions prior to 0.6.22 did not support Qt4, so enabling
+    # Qt4 should not be permitted when using a version of Avahi older
+    # than 0.6.22, hence the default to `false'.
+    let qt4Support = getConfig [ "avahi" "qt4Support" ] false;
+    in
+      selectVersion ../development/libraries/avahi "0.6.22" {
+	inherit stdenv fetchurl pkgconfig libdaemon dbus perl perlXMLParser
+	  expat lib;
+	inherit (gtkLibs) glib gtk;
+	inherit qt4Support;
+	qt4 = if qt4Support then qt4 else null;
+      };
 
   axel = import ../tools/networking/axel {
     inherit fetchurl stdenv;