diff --git a/app/src/main/java/eu/faircode/email/MessageHelper.java b/app/src/main/java/eu/faircode/email/MessageHelper.java
index e64c296ddc..db1e0ba8dd 100644
--- a/app/src/main/java/eu/faircode/email/MessageHelper.java
+++ b/app/src/main/java/eu/faircode/email/MessageHelper.java
@@ -751,7 +751,8 @@ public class MessageHelper {
             int sp = header.indexOf(" ");
             if (sp >= 0)
                 header = header.substring(0, sp); // "2 (High)"
-            header = header.trim();
+
+            header = header.replaceAll("[^A-Za-z0-9\\-]", "");
         }
 
         if ("high".equalsIgnoreCase(header) ||