diff --git a/resources/celerity/map.php b/resources/celerity/map.php
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -10,7 +10,7 @@
     'conpherence.pkg.css' => 'e68cf1fa',
     'conpherence.pkg.js' => '15191c65',
     'core.pkg.css' => '8be474cc',
-    'core.pkg.js' => 'e1f0f7bd',
+    'core.pkg.js' => 'e452721e',
     'differential.pkg.css' => '06dc617c',
     'differential.pkg.js' => 'c2ca903a',
     'diffusion.pkg.css' => 'a2d17c7d',
@@ -259,7 +259,7 @@
     'rsrc/externals/javelin/lib/__tests__/URI.js' => '1e45fda9',
     'rsrc/externals/javelin/lib/__tests__/behavior.js' => '1ea62783',
     'rsrc/externals/javelin/lib/behavior.js' => '61cbc29a',
-    'rsrc/externals/javelin/lib/control/tokenizer/Tokenizer.js' => '8d3bc1b2',
+    'rsrc/externals/javelin/lib/control/tokenizer/Tokenizer.js' => 'dfaf006b',
     'rsrc/externals/javelin/lib/control/typeahead/Typeahead.js' => '70baed2f',
     'rsrc/externals/javelin/lib/control/typeahead/normalizer/TypeaheadNormalizer.js' => '185bbd53',
     'rsrc/externals/javelin/lib/control/typeahead/source/TypeaheadCompositeSource.js' => '503e17fd',
@@ -710,7 +710,7 @@
     'javelin-scrollbar' => '9065f639',
     'javelin-sound' => '949c0fe5',
     'javelin-stratcom' => '327f418a',
-    'javelin-tokenizer' => '8d3bc1b2',
+    'javelin-tokenizer' => 'dfaf006b',
     'javelin-typeahead' => '70baed2f',
     'javelin-typeahead-composite-source' => '503e17fd',
     'javelin-typeahead-normalizer' => '185bbd53',
@@ -1573,12 +1573,6 @@
       'javelin-stratcom',
       'javelin-behavior',
     ),
-    '8d3bc1b2' => array(
-      'javelin-dom',
-      'javelin-util',
-      'javelin-stratcom',
-      'javelin-install',
-    ),
     '8d4a8c72' => array(
       'javelin-install',
       'javelin-dom',
@@ -2025,6 +2019,12 @@
       'phuix-icon-view',
       'phabricator-prefab',
     ),
+    'dfaf006b' => array(
+      'javelin-dom',
+      'javelin-util',
+      'javelin-stratcom',
+      'javelin-install',
+    ),
     'e1d25dfb' => array(
       'javelin-behavior',
       'javelin-stratcom',
diff --git a/src/applications/paste/conduit/PasteCreateConduitAPIMethod.php b/src/applications/paste/conduit/PasteCreateConduitAPIMethod.php
--- a/src/applications/paste/conduit/PasteCreateConduitAPIMethod.php
+++ b/src/applications/paste/conduit/PasteCreateConduitAPIMethod.php
@@ -64,9 +64,12 @@
       ->setTransactionType(PhabricatorPasteTitleTransaction::TRANSACTIONTYPE)
       ->setNewValue($title);
 
-    $xactions[] = id(new PhabricatorPasteTransaction())
-      ->setTransactionType(PhabricatorPasteLanguageTransaction::TRANSACTIONTYPE)
-      ->setNewValue($language);
+    if (strlen($language)) {
+      $xactions[] = id(new PhabricatorPasteTransaction())
+        ->setTransactionType(
+          PhabricatorPasteLanguageTransaction::TRANSACTIONTYPE)
+        ->setNewValue($language);
+    }
 
     $editor = id(new PhabricatorPasteEditor())
       ->setActor($viewer)
diff --git a/src/applications/paste/xaction/PhabricatorPasteLanguageTransaction.php b/src/applications/paste/xaction/PhabricatorPasteLanguageTransaction.php
--- a/src/applications/paste/xaction/PhabricatorPasteLanguageTransaction.php
+++ b/src/applications/paste/xaction/PhabricatorPasteLanguageTransaction.php
@@ -38,4 +38,20 @@
       $this->renderLanguageValue($this->getNewValue()));
   }
 
+  public function validateTransactions($object, array $xactions) {
+    $errors = array();
+
+    foreach ($xactions as $xaction) {
+      $new = $xaction->getNewValue();
+
+      if ($new !== null && !strlen($new)) {
+        $errors[] = $this->newInvalidError(
+          pht('Paste language must be null or a nonempty string.'),
+          $xaction);
+      }
+    }
+
+    return $errors;
+  }
+
 }
diff --git a/webroot/rsrc/externals/javelin/lib/control/tokenizer/Tokenizer.js b/webroot/rsrc/externals/javelin/lib/control/tokenizer/Tokenizer.js
--- a/webroot/rsrc/externals/javelin/lib/control/tokenizer/Tokenizer.js
+++ b/webroot/rsrc/externals/javelin/lib/control/tokenizer/Tokenizer.js
@@ -395,8 +395,12 @@
           break;
         case 'delete':
           if (!this._focus.value.length) {
+            // In unusual cases, it's possible for us to end up with a token
+            // that has the empty string ("") as a value. Support removal of
+            // this unusual token.
+
             var tok;
-            while ((tok = this._tokens.pop())) {
+            while ((tok = this._tokens.pop()) !== null) {
               if (this._remove(tok, true)) {
                 break;
               }