diff --git a/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MessageExtractor.java b/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MessageExtractor.java
index f0ab570e5..7d1b6e291 100644
--- a/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MessageExtractor.java
+++ b/k9mail-library/src/main/java/com/fsck/k9/mail/internet/MessageExtractor.java
@@ -166,6 +166,8 @@ public class MessageExtractor {
                 Html html = new Html(part);
                 viewables.add(html);
             }
+        } else if (part.getMimeType().equalsIgnoreCase("application/pgp-signature")) {
+            // ignore this type explicitly
         } else {
             // Everything else is treated as attachment.
             attachments.add(part);