diff --git a/content/bookmarks.js b/content/bookmarks.js
index 94918b10..38f70c2d 100644
--- a/content/bookmarks.js
+++ b/content/bookmarks.js
@@ -322,7 +322,7 @@ function Bookmarks() //{{{
         },
         {
             bang: true,
-            completer: function (filter) completion.bookmark(filter),
+            completer: function (context) completion.bookmark(context.filter),
             options: [[["-tags", "-T"], commands.OPTION_LIST]]
         });
 
@@ -335,7 +335,7 @@ function Bookmarks() //{{{
 
             liberator.echo(deletedCount + " bookmark(s) with url `" + url + "' deleted", commandline.FORCE_SINGLELINE);
         },
-        { completer: function (filter) completion.bookmark(filter) });
+        { completer: function (context) completion.bookmark(context.filter) });
 
     /////////////////////////////////////////////////////////////////////////////}}}
     ////////////////////// PUBLIC SECTION //////////////////////////////////////////
@@ -623,8 +623,9 @@ function History() //{{{
         },
         {
             bang: true,
-            completer: function (filter)
+            completer: function (context)
             {
+                let filter = context.filter;
                 var sh = getWebNavigation().sessionHistory;
                 var completions = [];
                 for (let i = sh.index - 1; i >= 0; i--)
@@ -673,8 +674,9 @@ function History() //{{{
         },
         {
             bang: true,
-            completer: function (filter)
+            completer: function (context)
             {
+                let filter = context.filter;
                 var sh = getWebNavigation().sessionHistory;
                 var completions = [];
                 for (let i = sh.index + 1; i < sh.count; i++)
diff --git a/content/buffer.js b/content/buffer.js
index 57c0c41b..edf158b3 100644
--- a/content/buffer.js
+++ b/content/buffer.js
@@ -512,7 +512,7 @@ function Buffer() //{{{
 
             stylesheetSwitchAll(window.content, args);
         },
-        { completer: function (filter) completion.alternateStylesheet(filter) });
+        { completer: function (context) completion.alternateStylesheet(context.filter) });
 
     commands.add(["re[load]"],
         "Reload current page",
@@ -564,7 +564,7 @@ function Buffer() //{{{
         {
             argCount: "?",
             bang: true,
-            completer: function (filter, bang, args, context) completion.file(context)
+            completer: function (context) completion.file(context)
         });
 
     commands.add(["st[op]"],
@@ -578,7 +578,7 @@ function Buffer() //{{{
         {
             argCount: "?",
             bang: true,
-            completer: function (filter, bang, args, context) completion.url(context, "bhf")
+            completer: function (context) completion.url(context, "bhf")
         });
 
     commands.add(["zo[om]"],
diff --git a/content/commands.js b/content/commands.js
index 5db8f0d2..f6ea3fd3 100644
--- a/content/commands.js
+++ b/content/commands.js
@@ -825,7 +825,7 @@ function Commands() //{{{
         {
             argCount: "2",
             bang: true,
-            completer: function (filter) completion.userCommand(filter),
+            completer: function (context) completion.userCommand(context.filter),
             options: [
                 [["-nargs"], commandManager.OPTION_STRING,
                      function (arg) /^[01*?+]$/.test(arg), ["0", "1", "*", "?", "+"]],
@@ -873,7 +873,7 @@ function Commands() //{{{
         },
         {
             argCount: "1",
-            completer: function (filter) completion.userCommand(filter)
+            completer: function (context) completion.userCommand(context.filter)
         });
 
     //}}}
diff --git a/content/completion.js b/content/completion.js
index 6933ec3d..5af617e7 100644
--- a/content/completion.js
+++ b/content/completion.js
@@ -1080,7 +1080,7 @@ function Completion() //{{{
                 if (args)
                 {
                     // XXX, XXX, XXX
-                    compObject = command.completer.call(command, args.string, special, args, context);
+                    compObject = command.completer.call(command, context, args, special, count);
                     if (compObject instanceof Array) // for now at least, let completion functions return arrays instead of objects
                         compObject = { start: compObject[0], items: compObject[1] };
                     if (args.completions)
diff --git a/content/events.js b/content/events.js
index a384d60e..a15819f1 100644
--- a/content/events.js
+++ b/content/events.js
@@ -114,7 +114,7 @@ function AutoCommands() //{{{
         {
             argCount: "3",
             bang: true,
-            completer: function (filter) completion.autocmdEvent(filter),
+            completer: function (context) completion.autocmdEvent(context.filter),
             literal: true
         });
 
@@ -127,7 +127,7 @@ function AutoCommands() //{{{
         },
         {
             argCount: "+",
-            completer: function (filter) completion.autocmdEvent(filter)
+            completer: function (context) completion.autocmdEvent(context.filter)
         }
     );
 
@@ -164,7 +164,7 @@ function AutoCommands() //{{{
         {
             // TODO: Vim actually just displays "No matching autocommands" when no arg is specified
             argCount: "+",
-            completer: function (filter) completion.autocmdEvent(filter)
+            completer: function (context) completion.autocmdEvent(context.filter)
         }
     );
 
@@ -719,7 +719,7 @@ function Events() //{{{
         },
         {
             bang: true,
-            completer: function (filter) completion.macro(filter)
+            completer: function (context) completion.macro(context.filter)
         });
 
     commands.add(["macros"],
@@ -730,14 +730,14 @@ function Events() //{{{
             var str = template.tabular(["Macro", "Keys"], [], events.getMacros(args.string));
             liberator.echo(str, commandline.FORCE_MULTILINE);
         },
-        { completer: function (filter) completion.macro(filter) });
+        { completer: function (context) completion.macro(context.filter) });
 
     commands.add(["pl[ay]"],
         "Replay a recorded macro",
         function (args) { events.playMacro(args.arguments[0]); },
         {
             argCount: "1",
-            completer: function (filter) completion.macro(filter)
+            completer: function (context) completion.macro(context.filter)
         });
 
     /////////////////////////////////////////////////////////////////////////////}}}
diff --git a/content/io.js b/content/io.js
index cdb30a99..c85e957a 100644
--- a/content/io.js
+++ b/content/io.js
@@ -208,7 +208,7 @@ function IO() //{{{
         },
         {
             argCount: "?",
-            completer: function (filter, bang, args, context) completion.file(context, true),
+            completer: function (context) completion.file(context, true),
             literal: true
         });
 
@@ -268,7 +268,7 @@ function IO() //{{{
         {
             argCount: "?",
             bang: true,
-            completer: function (filter, bang, args, context) completion.file(context, true)
+            completer: function (context) completion.file(context, true)
         });
 
     commands.add(["runt[ime]"],
@@ -301,7 +301,7 @@ function IO() //{{{
         {
             argCount: "1",
             bang: true,
-            completer: function (filter, bang, args, context) completion.file(context, true)
+            completer: function (context) completion.file(context, true)
         });
 
     commands.add(["!", "run"],
@@ -339,7 +339,7 @@ function IO() //{{{
         },
         {
             bang: true,
-            completer: function (filter) completion.shellCommand(filter)
+            completer: function (context) completion.shellCommand(filter)
         });
 
     /////////////////////////////////////////////////////////////////////////////}}}
diff --git a/content/liberator.js b/content/liberator.js
index 533e7894..fcb3985a 100644
--- a/content/liberator.js
+++ b/content/liberator.js
@@ -202,7 +202,7 @@ const liberator = (function () //{{{
             {
                 argCount: "1",
                 bang: true,
-                completer: function (filter) completion.dialog(filter)
+                completer: function (context) completion.dialog(context.filter)
             });
 
         // TODO: move this
@@ -257,10 +257,10 @@ const liberator = (function () //{{{
             {
                 argCount: "+", // NOTE: single arg may contain unescaped whitespace
                 // TODO: add this as a standard menu completion function
-                completer: function (filter)
+                completer: function (context)
                 {
                     let completions = getMenuItems().map(function (item) [item.fullMenuPath, item.label]);
-                    return [0, completion.filter(completions, filter)];
+                    return [0, completion.filter(completions, context.filter)];
                 }
             });
 
@@ -307,7 +307,7 @@ const liberator = (function () //{{{
             },
             {
                 bang: true,
-                completer: function (filter) completion.help(filter)
+                completer: function (context) completion.help(context.filter)
             });
 
         commands.add(["javas[cript]", "js"],
@@ -334,7 +334,7 @@ const liberator = (function () //{{{
             },
             {
                 bang: true,
-                completer: function (filter, bang, args, context) completion.javascript(context),
+                completer: function (context) completion.javascript(context),
                 hereDoc: true
             });
 
@@ -461,12 +461,12 @@ const liberator = (function () //{{{
             {
                 argCount: "+",
                 bang: true,
-                completer: function (filter)
+                completer: function (context)
                 {
-                    if (/^:/.test(filter))
-                        return completion.ex(filter);
+                    if (/^:/.test(context.filter))
+                        return completion.ex(context);
                     else
-                        return completion.javascript(filter);
+                        return completion.javascript(context);
                 },
                 count: true
             });
diff --git a/content/mail.js b/content/mail.js
index b7f5234b..07632bf9 100644
--- a/content/mail.js
+++ b/content/mail.js
@@ -684,7 +684,7 @@ function Mail() //{{{
                 SelectFolder(folder.URI);
         },
         {
-            completer: function (filter) getFolderCompletions(filter),
+            completer: function (context) getFolderCompletions(context.filter),
             count: true
         });
 
@@ -726,12 +726,12 @@ function Mail() //{{{
     commands.add(["copy[to]"],
         "Copy selected messages",
         function (args) { moveOrCopy(true, args.string); },
-        { completer: function (filter) getFolderCompletions(filter) });
+        { completer: function (context) getFolderCompletions(context.filter) });
 
     commands.add(["move[to]"],
         "Move selected messages",
         function (args) { moveOrCopy(false, args.string); },
-        { completer: function (filter) getFolderCompletions(filter) });
+        { completer: function (context) getFolderCompletions(context.filter) });
 
     commands.add(["empty[trash]"],
         "Empty trash of the current account",
diff --git a/content/mappings.js b/content/mappings.js
index 47b355e1..87e08c10 100644
--- a/content/mappings.js
+++ b/content/mappings.js
@@ -186,7 +186,7 @@ function Mappings() //{{{
 
         const opts = {
                 argCount: "2",
-                completer: function (filter) completion.userMapping(filter, modes),
+                completer: function (context) completion.userMapping(context.filter, modes),
                 options: [
                     [["<silent>", "<Silent>"],  commands.OPTION_NOARG]
                 ],
@@ -245,7 +245,7 @@ function Mappings() //{{{
                 if (!found)
                     liberator.echoerr("E31: No such mapping");
             },
-            { completer: function (filter) completion.userMapping(filter, modes) });
+            { completer: function (context) completion.userMapping(context.filter, modes) });
     }
 
     /////////////////////////////////////////////////////////////////////////////}}}
diff --git a/content/options.js b/content/options.js
index 97c9ac86..a44cc563 100644
--- a/content/options.js
+++ b/content/options.js
@@ -394,9 +394,9 @@ function Options() //{{{
         {
             bang: true,
             count: true,
-            completer: function (filter, special, count)
+            completer: function (context, args, special, count)
             {
-                return commands.get("set").completer(filter, special, count, { scope: options.OPTION_SCOPE_LOCAL });
+                return commands.get("set").completer(context.filter, special, count, { scope: options.OPTION_SCOPE_LOCAL });
             }
         }
     );
@@ -410,9 +410,9 @@ function Options() //{{{
         {
             bang: true,
             count: true,
-            completer: function (filter, special, count)
+            completer: function (context, args, special, count)
             {
-                return commands.get("set").completer(filter, special, count, { scope: options.OPTION_SCOPE_GLOBAL });
+                return commands.get("set").completer(context.filter, special, count, { scope: options.OPTION_SCOPE_GLOBAL });
             }
         }
     );
@@ -686,7 +686,7 @@ function Options() //{{{
         },
         {
             bang: true,
-            completer: function (filter, special, count, modifiers)
+            completer: function (context, args, special, count, modifiers)
             {
                 var optionCompletions = [];
 
diff --git a/content/style.js b/content/style.js
index d8af138a..fb08a574 100644
--- a/content/style.js
+++ b/content/style.js
@@ -389,7 +389,7 @@ liberator.registerObserver("load_commands", function ()
         },
         {
             argCount: 1,
-            completer: function (filter) completion.colorScheme(filter)
+            completer: function (context) completion.colorScheme(context.filter)
         });
 
     commands.add(["sty[le]"],
@@ -430,7 +430,7 @@ liberator.registerObserver("load_commands", function ()
         {
             argCount: "2",
             bang: true,
-            completer: function (filter, bang, args) {
+            completer: function (context, args, bang) {
                 let compl = [];
                 if (args.completeArg == 0)
                 {
@@ -467,12 +467,13 @@ liberator.registerObserver("load_commands", function ()
         },
         {
             argCount: "2",
-            completer: function (filter) [0, completion.filter(
+            // FIXME: Ugly.
+            completer: function (context) [0, completion.filter(
                     [[i, <>{s.sites.join(",")}: {s.css.replace("\n", "\\n")}</>]
                         for ([i, s] in styles.userSheets)
                     ]
                     .concat([[s, ""] for each (s in styles.sites)])
-                    , filter)],
+                    , context.filter)],
             literal: true,
             options: [[["-index", "-i"], commands.OPTION_INT, null, function () [[k, v.name || v.sites.join(",") + " " + v.css] for ([k, v] in Iterator(styles.userNames))]],
                       [["-name", "-n"],  commands.OPTION_STRING, null, function () [[k, v.css] for ([k, v] in Iterator(styles.userNames))]]]
@@ -513,9 +514,8 @@ liberator.registerObserver("load_commands", function ()
             argCount: "2",
             bang: true,
             // TODO: add this as a standard highlight completion function?
-            // I agree. It could (should) be much more sophisticated. --Kris
-            completer: function (filter) [0,
-                    completion.filter([[v.class, ""] for (v in highlight)], filter)
+            completer: function (context) [0,
+                    completion.filter([[v.class, ""] for (v in highlight)], context.filter)
                 ],
             hereDoc: true,
             literal: true,
diff --git a/content/tabs.js b/content/tabs.js
index 62a4e3e1..01759507 100644
--- a/content/tabs.js
+++ b/content/tabs.js
@@ -354,7 +354,7 @@ function Tabs() //{{{
         {
             bang: true,
             count: true,
-            completer: function (filter) completion.buffer(filter)
+            completer: function (context) completion.buffer(context.filter)
         });
 
     // TODO: this should open in a new tab positioned directly after the current one, not at the end
@@ -368,7 +368,7 @@ function Tabs() //{{{
         },
         {
             argCount: "+",
-            completer: function (filter) completion.ex(filter)
+            completer: function (context) completion.ex(context.filter)
         });
 
     commands.add(["tabl[ast]", "bl[ast]"],
@@ -478,7 +478,7 @@ function Tabs() //{{{
             {
                 bang: true,
                 count: true,
-                completer: function (filter) completion.buffer(filter)
+                completer: function (context) completion.buffer(context.filter)
             });
 
         commands.add(["buffers", "files", "ls", "tabs"],
@@ -548,7 +548,7 @@ function Tabs() //{{{
             },
             {
                 bang: true,
-                completer: function (filter, bang, args, context) completion.url(context)
+                completer: function (context) completion.url(context)
             });
 
         commands.add(["tabde[tach]"],
@@ -618,7 +618,7 @@ function Tabs() //{{{
                 undoCloseTab(count - 1);
             },
             {
-                completer: function (filter)
+                completer: function (context)
                 {
                     // get closed-tabs from nsSessionStore
                     var ss = Components.classes["@mozilla.org/browser/sessionstore;1"]
@@ -629,7 +629,7 @@ function Tabs() //{{{
                     {
                         var url = undoItems[i].state.entries[0].url;
                         var title = undoItems[i].title;
-                        if (completion.match([url, title], filter, false))
+                        if (completion.match([url, title], context.filter, false))
                             completions.push([url, title]);
                     }
                     return [0, completions];
diff --git a/content/ui.js b/content/ui.js
index 2be9b50c..af2746d5 100644
--- a/content/ui.js
+++ b/content/ui.js
@@ -500,7 +500,7 @@ function CommandLine() //{{{
                 if (str != null)
                     command.action(str);
             },
-            { completer: function (filter, bang, args, context) completion.javascript(context) });
+            { completer: function (context) completion.javascript(context) });
     });
 
     commands.add(["mes[sages]"],
diff --git a/content/vimperator.js b/content/vimperator.js
index 5e0607d3..b4c11526 100644
--- a/content/vimperator.js
+++ b/content/vimperator.js
@@ -293,7 +293,7 @@ const config = { //{{{
             },
             {
                 bang: true,
-                completer: function (filter, args, bang, context) completion.url(context)
+                completer: function (context) completion.url(context)
             });
 
         commands.add(["redr[aw]"],
@@ -345,7 +345,7 @@ const config = { //{{{
             },
             {
                 argCount: "+",
-                completer: function (filter) completion.sidebar(filter)
+                completer: function (context) completion.sidebar(context.filter)
             });
 
         commands.add(["winc[lose]", "wc[lose]"],
@@ -364,7 +364,7 @@ const config = { //{{{
                 else
                     liberator.open("about:blank", liberator.NEW_WINDOW);
             },
-            { completer: function (filter, bang, args, context) completion.url(context) });
+            { completer: function (context) completion.url(context) });
 
         /////////////////////////////////////////////////////////////////////////////}}}
         ////////////////////// OPTIONS /////////////////////////////////////////////////