diff --git a/src/applications/differential/customfield/DifferentialAsanaRepresentationField.php b/src/applications/differential/customfield/DifferentialAsanaRepresentationField.php
--- a/src/applications/differential/customfield/DifferentialAsanaRepresentationField.php
+++ b/src/applications/differential/customfield/DifferentialAsanaRepresentationField.php
@@ -44,6 +44,10 @@
 
     $edge = head($edges[$src_phid][$edge_type]);
 
+    if (!$edge) {
+      return null;
+    }
+
     if (!empty($edge['data']['gone'])) {
       return phutil_tag(
         'em',
diff --git a/src/applications/differential/parser/DifferentialChangesetParser.php b/src/applications/differential/parser/DifferentialChangesetParser.php
--- a/src/applications/differential/parser/DifferentialChangesetParser.php
+++ b/src/applications/differential/parser/DifferentialChangesetParser.php
@@ -1326,9 +1326,15 @@
     $old_back = array();
     $new_back = array();
     foreach ($this->old as $ii => $old) {
+      if ($old === null) {
+        continue;
+      }
       $old_back[$old['line']] = $old['line'];
     }
     foreach ($this->new as $ii => $new) {
+      if ($new === null) {
+        continue;
+      }
       $new_back[$new['line']] = $new['line'];
     }
 
diff --git a/src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php b/src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php
--- a/src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php
+++ b/src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php
@@ -593,9 +593,14 @@
 
       $map = array();
       foreach ($new as $offset => $new_line) {
+        if ($new_line === null) {
+          continue;
+        }
+
         if ($new_line['line'] === null) {
           continue;
         }
+
         $map[$new_line['line']] = $offset;
       }