diff --git a/resources/celerity/map.php b/resources/celerity/map.php
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -8,7 +8,7 @@
   'names' =>
   array(
     'core.pkg.css' => 'fb144113',
-    'core.pkg.js' => 'd3fecc57',
+    'core.pkg.js' => 'e39d336b',
     'darkconsole.pkg.js' => 'ca8671ce',
     'differential.pkg.css' => 'cc216438',
     'differential.pkg.js' => '11a5b750',
@@ -463,7 +463,7 @@
     'rsrc/js/core/behavior-line-linker.js' => 'bc778103',
     'rsrc/js/core/behavior-more.js' => '9b9197be',
     'rsrc/js/core/behavior-object-selector.js' => 'b4eef37b',
-    'rsrc/js/core/behavior-oncopy.js' => 'dab9253e',
+    'rsrc/js/core/behavior-oncopy.js' => 'c3e218fe',
     'rsrc/js/core/behavior-phabricator-nav.js' => 'b5842a5e',
     'rsrc/js/core/behavior-phabricator-remarkup-assist.js' => 'c021950a',
     'rsrc/js/core/behavior-refresh-csrf.js' => 'c4b31646',
@@ -596,7 +596,7 @@
     'javelin-behavior-phabricator-nav' => 'b5842a5e',
     'javelin-behavior-phabricator-notification-example' => 'c51a6616',
     'javelin-behavior-phabricator-object-selector' => 'b4eef37b',
-    'javelin-behavior-phabricator-oncopy' => 'dab9253e',
+    'javelin-behavior-phabricator-oncopy' => 'c3e218fe',
     'javelin-behavior-phabricator-remarkup-assist' => 'c021950a',
     'javelin-behavior-phabricator-reveal-content' => '8f24abfc',
     'javelin-behavior-phabricator-search-typeahead' => 'f6b56f7a',
@@ -1634,6 +1634,11 @@
       2 => 'javelin-util',
       3 => 'javelin-magical-init',
     ),
+    'c3e218fe' =>
+    array(
+      0 => 'javelin-behavior',
+      1 => 'javelin-dom',
+    ),
     'c4b31646' =>
     array(
       0 => 'javelin-request',
@@ -1768,11 +1773,6 @@
       1 => 'javelin-util',
       2 => 'javelin-stratcom',
     ),
-    'dab9253e' =>
-    array(
-      0 => 'javelin-behavior',
-      1 => 'javelin-dom',
-    ),
     'dd7e8ef5' =>
     array(
       0 => 'javelin-behavior',
diff --git a/webroot/rsrc/js/core/behavior-oncopy.js b/webroot/rsrc/js/core/behavior-oncopy.js
--- a/webroot/rsrc/js/core/behavior-oncopy.js
+++ b/webroot/rsrc/js/core/behavior-oncopy.js
@@ -18,63 +18,48 @@
 
   var zws = "\u200B"; // Unicode Zero-Width Space
 
-  document.body.oncopy = function(e) {
+  JX.enableDispatch(document.body, 'copy');
+  JX.Stratcom.listen(
+    ['copy'],
+    null,
+    function(e) {
 
-    var selection = window.getSelection();
-    var text = selection.toString();
-
-    if (text.indexOf(zws) == -1) {
-      // If there's no marker in the text, just let it copy normally.
-      return;
-    }
-
-    var result = [];
-
-    // Strip everything before the marker (and the marker itself) out of the
-    // text. If a line doesn't have the marker, throw it away (the assumption
-    // is that it's a line number or part of some other meta-text).
-    var lines = text.split("\n");
-    var pos;
-    for (var ii = 0; ii < lines.length; ii++) {
-      pos = lines[ii].indexOf(zws);
-      if (pos == -1 && ii !== 0) {
-        continue;
+      var selection;
+      var text;
+      if (window.getSelection) {
+        selection = window.getSelection();
+        text = selection.toString();
+      } else {
+        selection = document.selection;
+        text = selection.createRange().text;
       }
-      result.push(lines[ii].substring(pos + 1));
-    }
-    result = result.join("\n");
-
-    if (e.clipboardData) {
-      // Safari and Chrome support this easy, straightforward mechanism.
-      e.clipboardData.setData('Text', result);
-      e.preventDefault();
-    } else {
 
-      // In Firefox, we have to create a <pre> and select the text in it, then
-      // let the copy event fire. It has to be a <pre> because Firefox won't
-      // copy returns properly out of a div, even if it has 'whitespace: pre'.
-      // There's been a bug open for 10 (!) years:
-      //
-      //   https://bugzilla.mozilla.org/show_bug.cgi?id=116083
-
-      var style = {
-        position: 'absolute',
-        left:     '-10000px'
-      };
-      var pre = JX.$N('pre', {style: style}, result);
-      document.body.appendChild(pre);
+      if (text.indexOf(zws) == -1) {
+        // If there's no marker in the text, just let it copy normally.
+        return;
+      }
 
-      // Select the text in the <pre>.
-      var range = document.createRange();
-      range.selectNodeContents(pre);
-      selection.removeAllRanges();
-      selection.addRange(range);
+      var result = [];
 
-      setTimeout(function() { JX.DOM.remove(pre); }, 0);
+      // Strip everything before the marker (and the marker itself) out of the
+      // text. If a line doesn't have the marker, throw it away (the assumption
+      // is that it's a line number or part of some other meta-text).
+      var lines = text.split("\n");
+      var pos;
+      for (var ii = 0; ii < lines.length; ii++) {
+        pos = lines[ii].indexOf(zws);
+        if (pos == -1 && ii !== 0) {
+          continue;
+        }
+        result.push(lines[ii].substring(pos + 1));
+      }
+      result = result.join("\n");
 
-      // TODO: I tried to restore the old selection range but it doesn't seem
-      // to work or give me any errors. So you lose your selection when you
-      // copy. Oh well?
-    }
-  };
+      var rawEvent = e.getRawEvent();
+      var clipboardData = 'clipboardData' in rawEvent ?
+        rawEvent.clipboardData :
+        window.clipboardData;
+      clipboardData.setData('Text', result);
+      e.prevent();
+    });
 });