diff --git a/Makefile b/Makefile
index e6f0f30..871ad28 100644
--- a/Makefile
+++ b/Makefile
@@ -165,7 +165,8 @@ substitute := perl -p -e 's/@([^@]+)@/defined $$ENV{$$1} ? $$ENV{$$1} : $$&/ge'
 
 # The variables to substitute for their values in .in files.
 export package_version update_url_tag package_url revision_id chrome_path \
-       channel extension_id
+       channel extension_id \
+       fx_min_version fx_max_version tb_min_version tb_max_version
 
 
 ################################################################################
@@ -207,7 +208,9 @@ uninstall:
 
 clean:
 	rm -f $(dotin_files) chrome.jar $(package_name)
-	$(MAKE) -C test/unit clean
+	@if [ -e "test/unit" ]; then \
+	  $(MAKE) -C test/unit clean; \
+	fi
 
 help:
 	@echo 'Targets:'
diff --git a/client.mk b/client.mk
index 7ce5cb1..4809f61 100644
--- a/client.mk
+++ b/client.mk
@@ -55,3 +55,8 @@ version           := 0.3
 site_url_base     := https://people.mozilla.com/~myk/snowl/dist
 site_path_local   := dist
 site_path_remote  := people.mozilla.com:/home/myk/public_html/snowl/dist
+
+# The minimum and maximum versions of Firefox with which the extension
+# is compatible.  These are used in both the install and update manifests.
+fx_min_version    := 3.5
+fx_max_version    := 3.6b1pre
diff --git a/defaults/preferences/prefs.js.in b/defaults/preferences/prefs.js.in
index 801f989..6f5faa5 100644
--- a/defaults/preferences/prefs.js.in
+++ b/defaults/preferences/prefs.js.in
@@ -1,5 +1,5 @@
 // About box description, so it's localizable
-pref("extensions.snowl@mozilla.org.description", "chrome://snowl/locale/about.properties");
+pref("extensions.@extension_id@.description", "chrome://snowl/locale/about.properties");
 
 // Header view pref: 0 = none, 1 = brief, 2 = full
 pref("extensions.snowl.message.headerView", 1);
diff --git a/install.rdf.in b/install.rdf.in
index 632f7d3..26fd1cc 100644
--- a/install.rdf.in
+++ b/install.rdf.in
@@ -4,7 +4,7 @@
      xmlns:em="http://www.mozilla.org/2004/em-rdf#">
 
   <Description about="urn:mozilla:install-manifest">
-    <em:id>snowl@mozilla.org</em:id>
+    <em:id>@extension_id@</em:id>
     <em:name>Snowl</em:name>
     <em:version>@package_version@</em:version>
     <em:description>conversations redelivered</em:description>
@@ -35,8 +35,8 @@
     <em:targetApplication> <!-- Firefox -->
       <Description>
         <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
-        <em:minVersion>3.5</em:minVersion>
-        <em:maxVersion>3.6a2pre</em:maxVersion>
+        <em:minVersion>@fx_min_version@</em:minVersion>
+        <em:maxVersion>@fx_max_version@</em:maxVersion>
       </Description>
     </em:targetApplication>
 
diff --git a/update.rdf.in b/update.rdf.in
index a1244a7..f7b5be0 100644
--- a/update.rdf.in
+++ b/update.rdf.in
@@ -2,7 +2,7 @@
 <RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:em="http://www.mozilla.org/2004/em-rdf#">
 
-<Description about="urn:mozilla:extension:snowl@mozilla.org">
+<Description about="urn:mozilla:extension:@extension_id@">
   <em:updates>
     <Seq>
       <li>
@@ -11,8 +11,8 @@
           <em:targetApplication> <!-- Firefox -->
             <Description>
               <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
-              <em:minVersion>3.5</em:minVersion>
-              <em:maxVersion>3.6a2pre</em:maxVersion>
+	      <em:minVersion>@fx_min_version@</em:minVersion>
+	      <em:maxVersion>@fx_max_version@</em:maxVersion>
               <em:updateLink>@package_url@</em:updateLink>
             </Description>
           </em:targetApplication>