diff --git a/common/content/buffer.js b/common/content/buffer.js
index a3fc1f81..a1f6fe94 100644
--- a/common/content/buffer.js
+++ b/common/content/buffer.js
@@ -1306,10 +1306,19 @@ var Buffer = Module("buffer", {
                 dactyl.assert(!arg || arg[0] == ">" && !util.OS.isWindows,
                               _("error.trailingCharacters"));
 
+                const PRINTER = "PostScript/default";
+                const BRANCH  = "print.printer_" + PRINTER + ".";
+
                 prefs.withContext(function () {
                     if (arg) {
-                        prefs.set("print.print_to_file", "true");
-                        prefs.set("print.print_to_filename", io.File(arg.substr(1)).path);
+                        prefs.set("print.print_printer", PRINTER);
+
+                        prefs.set(   "print.print_to_file", true);
+                        prefs.set(BRANCH + "print_to_file", true);
+
+                        prefs.set(   "print.print_to_filename", io.File(arg.substr(1)).path);
+                        prefs.set(BRANCH + "print_to_filename", io.File(arg.substr(1)).path);
+
                         dactyl.echomsg(_("print.toFile", arg.substr(1)));
                     }
                     else
diff --git a/common/modules/prefs.jsm b/common/modules/prefs.jsm
index 803f42c3..b546ce53 100644
--- a/common/modules/prefs.jsm
+++ b/common/modules/prefs.jsm
@@ -210,11 +210,8 @@ var Prefs = Module("prefs", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference])
      * @param {value} value The new preference value.
      */
     set: function (name, value) {
-        if (this._prefContexts.length) {
-            let val = this.get(name, null);
-            if (val != null)
-                this._prefContexts[this._prefContexts.length - 1][name] = val;
-        }
+        if (this._prefContexts.length)
+            this._prefContexts[this._prefContexts.length - 1][name] = this.get(name, null);
 
         function assertType(needType)
             util.assert(type === Ci.nsIPrefBranch.PREF_INVALID || type === needType,
@@ -240,7 +237,10 @@ var Prefs = Module("prefs", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference])
             this.branch.setBoolPref(name, value);
             break;
         default:
-            throw FailedAssertion("Unknown preference type: " + typeof value + " (" + name + "=" + value + ")");
+            if (value == null && this != this.defaults)
+                this.reset(name);
+            else
+                throw FailedAssertion("Unknown preference type: " + typeof value + " (" + name + "=" + value + ")");
         }
     },