diff --git a/content/completion.js b/content/completion.js
index b0592bf5..a333abef 100644
--- a/content/completion.js
+++ b/content/completion.js
@@ -1130,7 +1130,7 @@ function Completion() //{{{
             let list = template.generic(
                 <div highlight="Completions">
                     { template.completionRow(context.title, "CompTitle") }
-                    { template.map(context.items, function (item) context.createRow(item)) }
+                    { template.map(context.items, function (item) context.createRow(item), null, 50) }
                 </div>);
             commandline.echo(list, commandline.HL_NORMAL, commandline.FORCE_MULTILINE);
         },
diff --git a/content/template.js b/content/template.js
index 0d86f2b4..3d26df55 100644
--- a/content/template.js
+++ b/content/template.js
@@ -2,7 +2,7 @@ const template = {
     add: function add(a, b) a + b,
     join: function join(c) function (a, b) a + c + b,
 
-    map: function map(iter, fn, sep)
+    map: function map(iter, fn, sep, interruptable)
     {
         if (iter.length) /* Kludge? */
             iter = util.Array.iterator(iter);
@@ -15,6 +15,8 @@ const template = {
                 continue;
             if (sep && n++)
                 ret += sep;
+            if (interruptable && n % interruptable == 0)
+                liberator.threadYield(true, true);
             ret += val;
         }
         return ret;