diff --git a/src/infrastructure/PhabricatorRequestOverseer.php b/src/infrastructure/PhabricatorRequestOverseer.php
index dfa099a8c3..6ae4b8bdbc 100644
--- a/src/infrastructure/PhabricatorRequestOverseer.php
+++ b/src/infrastructure/PhabricatorRequestOverseer.php
@@ -31,11 +31,10 @@ final class PhabricatorRequestOverseer {
    * the request anyway, and provides no formal way to detect that this
    * happened.
    *
-   * We can still read the entire body out of `php://input`. However, this
-   * stream can't be rewound, and according to the documentation isn't available
-   * for "multipart/form-data" (on nginx + php-fpm it appears that it is
-   * available, though, at least) so any attempt to generate $_POST would create
-   * side effects and be fragile.
+   * We can still read the entire body out of `php://input`. However according
+   * to the documentation the stream isn't available for "multipart/form-data"
+   * (on nginx + php-fpm it appears that it is available, though, at least) so
+   * any attempt to generate $_POST would be fragile.
    */
   private function detectPostMaxSizeTriggered() {
     // If this wasn't a POST, we're fine.
@@ -48,6 +47,16 @@ final class PhabricatorRequestOverseer {
       return;
     }
 
+    // For HTML5 drag-and-drop file uploads, Safari submits the data as
+    // "application/x-www-form-urlencoded". For most files this generates
+    // something in POST because most files decode to some nonempty (albeit
+    // meaningless) value. However, some files (particularly small images)
+    // don't decode to anything. If we know this is a drag-and-drop upload,
+    // we can skip this check.
+    if (isset($_REQUEST['__upload__'])) {
+      return;
+    }
+
     // PHP generates $_POST only for two content types. This routing happens
     // in `main/php_content_types.c` in PHP. Normally, all forms use one of
     // these content types, but some requests may not -- for example, Firefox
diff --git a/webroot/rsrc/js/application/core/DragAndDropFileUpload.js b/webroot/rsrc/js/application/core/DragAndDropFileUpload.js
index 00c3c05ed9..d77e7c2986 100644
--- a/webroot/rsrc/js/application/core/DragAndDropFileUpload.js
+++ b/webroot/rsrc/js/application/core/DragAndDropFileUpload.js
@@ -107,6 +107,7 @@ JX.install('PhabricatorDragAndDropFileUpload', {
 
       var up_uri = JX.$U(this.getURI())
         .setQueryParam('name', file.getName())
+        .setQueryParam('__upload__', 1)
         .toString();
 
       var onupload = JX.bind(this, function(r) {
diff --git a/webroot/rsrc/js/application/core/PasteFileUpload.js b/webroot/rsrc/js/application/core/PasteFileUpload.js
index 2869087665..d3e7c79703 100644
--- a/webroot/rsrc/js/application/core/PasteFileUpload.js
+++ b/webroot/rsrc/js/application/core/PasteFileUpload.js
@@ -45,6 +45,7 @@ JX.install('PhabricatorPasteFileUpload', {
 
               var up_uri = JX.$U(this.getURI())
                 .setQueryParam('name', 'clipboard.png')
+                .setQueryParam('__upload__', 1)
                 .toString();
 
               new JX.Request(up_uri, JX.bind(this, function(r) {