diff --git a/conf/default.conf.php b/conf/default.conf.php
index 8b837d9be6..00e0c36cda 100644
--- a/conf/default.conf.php
+++ b/conf/default.conf.php
@@ -416,6 +416,12 @@ return array(
   // DifferentialCommitMessageModifier
   'differential.modify-commit-message-class' => null,
 
+  // List of file regexps were whitespace is meaningful and should not
+  // use 'ignore-all' by default
+  'differential.whitespace-matters' => array(
+    '/\.py$/',
+  ),
+
 
 // -- Maniphest ------------------------------------------------------------- //
 
diff --git a/src/applications/differential/parser/changeset/DifferentialChangesetParser.php b/src/applications/differential/parser/changeset/DifferentialChangesetParser.php
index 8e4b24b4ac..9d1b39d4a2 100644
--- a/src/applications/differential/parser/changeset/DifferentialChangesetParser.php
+++ b/src/applications/differential/parser/changeset/DifferentialChangesetParser.php
@@ -767,6 +767,10 @@ class DifferentialChangesetParser {
 
         $ignore_all = ($this->whitespaceMode == self::WHITESPACE_IGNORE_ALL);
 
+        if ($ignore_all && $changeset->getWhitespaceMatters()) {
+          $ignore_all = false;
+        }
+
         // The "ignore all whitespace" algorithm depends on rediffing the
         // files, and we currently need complete representations of both
         // files to do anything reasonable. If we only have parts of the files,
diff --git a/src/applications/differential/storage/changeset/DifferentialChangeset.php b/src/applications/differential/storage/changeset/DifferentialChangeset.php
index 758e311c8f..b8f398ab15 100644
--- a/src/applications/differential/storage/changeset/DifferentialChangeset.php
+++ b/src/applications/differential/storage/changeset/DifferentialChangeset.php
@@ -184,4 +184,15 @@ class DifferentialChangeset extends DifferentialDAO {
     return 80;
   }
 
+  public function getWhitespaceMatters() {
+    $config = PhabricatorEnv::getEnvConfig('differential.whitespace-matters');
+    foreach ($config as $regexp) {
+      if (preg_match($regexp, $this->getFileName())) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
 }
diff --git a/src/applications/differential/view/revisionupdatehistory/DifferentialRevisionUpdateHistoryView.php b/src/applications/differential/view/revisionupdatehistory/DifferentialRevisionUpdateHistoryView.php
index df14dfa595..c2711f588a 100644
--- a/src/applications/differential/view/revisionupdatehistory/DifferentialRevisionUpdateHistoryView.php
+++ b/src/applications/differential/view/revisionupdatehistory/DifferentialRevisionUpdateHistoryView.php
@@ -173,7 +173,7 @@ final class DifferentialRevisionUpdateHistoryView extends AphrontView {
       ));
 
     $options = array(
-      'ignore-all' => 'Ignore All',
+      'ignore-all' => 'Ignore Most',
       'ignore-trailing' => 'Ignore Trailing',
       'show-all' => 'Show All',
     );