diff --git a/src/applications/differential/customfield/DifferentialRequiredSignaturesField.php b/src/applications/differential/customfield/DifferentialRequiredSignaturesField.php
index 809d60573c..0daddf40cb 100644
--- a/src/applications/differential/customfield/DifferentialRequiredSignaturesField.php
+++ b/src/applications/differential/customfield/DifferentialRequiredSignaturesField.php
@@ -130,5 +130,17 @@ final class DifferentialRequiredSignaturesField
     return false;
   }
 
+  public function getWarningsForRevisionHeader(array $handles) {
+    if (!$this->haveAnyUnsignedDocuments()) {
+      return array();
+    }
+
+    return array(
+      pht(
+        'This revision can not be accepted until the required legal '.
+        'agreements have been signed.'),
+    );
+  }
+
 
 }