diff --git a/src/applications/differential/__tests__/data/generated.diff.one.unshielded b/src/applications/differential/__tests__/data/generated.diff.one.unshielded
--- a/src/applications/differential/__tests__/data/generated.diff.one.unshielded
+++ b/src/applications/differential/__tests__/data/generated.diff.one.unshielded
@@ -1,6 +1,6 @@
 N 1 . @generated\n~
 O 2 - \n~
-N 2 + \n~
 O 3 - This is a generated file.\n~
+N 2 + \n~
 N 3 + This is a generated file{(, full of generated code)}.\n~
 N 4 . \n~
diff --git a/src/applications/differential/__tests__/data/groups.diff b/src/applications/differential/__tests__/data/groups.diff
new file mode 100644
--- /dev/null
+++ b/src/applications/differential/__tests__/data/groups.diff
@@ -0,0 +1,16 @@
+diff --git a/style b/style
+index a5fc249..18edce4 100644
+--- a/style
++++ b/style
+@@ -57,8 +57,8 @@
+ .dashboard-panel div.phabricator-feed-frame {
+   background: #fff;
+   margin: 0;
+-  border-left: 1px solid {$lightblueborder};
+-  border-right: 1px solid {$lightblueborder};
+-  border-bottom: 1px solid {$blueborder};
++  border-back: 1px solid {$lightblueborder};
++  border-front: 1px solid {$lightblueborder};
++  border-inside: 1px solid {$blueborder};
+   max-width: none;
+ }
diff --git a/src/applications/differential/__tests__/data/groups.diff.one.expect b/src/applications/differential/__tests__/data/groups.diff.one.expect
new file mode 100644
--- /dev/null
+++ b/src/applications/differential/__tests__/data/groups.diff.one.expect
@@ -0,0 +1,17 @@
+CTYPE 2 1 (unforced)
+style
+style
+-
+X <MISSING-CONTEXT>
+N 57 . .dashboard-panel div.phabricator-feed-frame {\n~
+N 58 .   background: #fff;\n~
+N 59 .   margin: 0;\n~
+O 60 -   border-{(left)}: 1px solid {$lightblueborder};\n~
+O 61 -   border-{(righ)}t: 1px solid {$lightblueborder};\n~
+O 62 -   border-{(bottom)}: 1px solid {$blueborder};\n~
+N 60 +   border-{(back)}: 1px solid {$lightblueborder};\n~
+N 61 +   border-{(fron)}t: 1px solid {$lightblueborder};\n~
+N 62 +   border-{(inside)}: 1px solid {$blueborder};\n~
+N 63 .   max-width: none;\n~
+N 64 . }\n~
+X <MISSING-CONTEXT>
diff --git a/src/applications/differential/__tests__/data/groups.diff.two.expect b/src/applications/differential/__tests__/data/groups.diff.two.expect
new file mode 100644
--- /dev/null
+++ b/src/applications/differential/__tests__/data/groups.diff.two.expect
@@ -0,0 +1,22 @@
+CTYPE 2 1 (unforced)
+style
+style
+-
+X <MISSING-CONTEXT>
+O 57 . .dashboard-panel div.phabricator-feed-frame {\n~
+N 57 . .dashboard-panel div.phabricator-feed-frame {\n~
+O 58 .   background: #fff;\n~
+N 58 .   background: #fff;\n~
+O 59 .   margin: 0;\n~
+N 59 .   margin: 0;\n~
+O 60 -   border-{(left)}: 1px solid {$lightblueborder};\n~
+N 60 +   border-{(back)}: 1px solid {$lightblueborder};\n~
+O 61 -   border-{(righ)}t: 1px solid {$lightblueborder};\n~
+N 61 +   border-{(fron)}t: 1px solid {$lightblueborder};\n~
+O 62 -   border-{(bottom)}: 1px solid {$blueborder};\n~
+N 62 +   border-{(inside)}: 1px solid {$blueborder};\n~
+O 63 .   max-width: none;\n~
+N 63 .   max-width: none;\n~
+O 64 . }\n~
+N 64 . }\n~
+X <MISSING-CONTEXT>
diff --git a/src/applications/differential/render/DifferentialChangesetRenderer.php b/src/applications/differential/render/DifferentialChangesetRenderer.php
--- a/src/applications/differential/render/DifferentialChangesetRenderer.php
+++ b/src/applications/differential/render/DifferentialChangesetRenderer.php
@@ -503,10 +503,6 @@
           // Ignore it when rendering a one-up diff.
           continue;
         }
-        if ($new_buf) {
-          $out[] = $new_buf;
-          $new_buf = array();
-        }
         $old_buf[] = $primitive;
       } else if ($type == 'new') {
         if ($primitive['line'] === null) {
@@ -514,17 +510,16 @@
           // old file. Ignore it when rendering a one-up diff.
           continue;
         }
-        if ($old_buf) {
-          $out[] = $old_buf;
-          $old_buf = array();
-        }
         if (!$primitive['htype']) {
           // If this line is the same in both versions of the file, put it in
           // the old line buffer. This makes sure inlines on old, unchanged
           // lines end up in the right place.
 
-          // First, we need to flush the new line buffer if there's anything
-          // in it.
+          // First, we need to flush the line buffers if they're not empty.
+          if ($old_buf) {
+            $out[] = $old_buf;
+            $old_buf = array();
+          }
           if ($new_buf) {
             $out[] = $new_buf;
             $new_buf = array();
@@ -545,15 +540,15 @@
         if (!$primitive['right']) {
           $out[] = $old_buf;
           $out[] = array($primitive);
-          $out[] = $new_buf;
+          $old_buf = array();
         } else {
           $out[] = $old_buf;
           $out[] = $new_buf;
           $out[] = array($primitive);
+          $old_buf = array();
+          $new_buf = array();
         }
 
-        $old_buf = array();
-        $new_buf = array();
       } else {
         throw new Exception("Unknown primitive type '{$primitive}'!");
       }