diff --git a/k9mail/src/main/java/com/fsck/k9/ui/messageview/MessageCryptoPresenter.java b/k9mail/src/main/java/com/fsck/k9/ui/messageview/MessageCryptoPresenter.java
index 3f2c070a1e32da9d14ae513e0a65deed2dba93d8..388cbbbda19adf55983f8e642bebcae666bf98c2 100644
--- a/k9mail/src/main/java/com/fsck/k9/ui/messageview/MessageCryptoPresenter.java
+++ b/k9mail/src/main/java/com/fsck/k9/ui/messageview/MessageCryptoPresenter.java
@@ -91,6 +91,11 @@ public class MessageCryptoPresenter implements OnCryptoClickListener {
                         R.string.messageview_crypto_warning_error);
                 break;
             }
+            case ENCRYPTED_UNSIGNED: {
+                showMessageCryptoWarning(messageView, account, messageViewInfo,
+                        R.string.messageview_crypto_warning_unsigned);
+                break;
+            }
 
             case CANCELLED: {
                 Drawable providerIcon = getOpenPgpApiProviderIcon(messageView.getContext(), account);
diff --git a/k9mail/src/main/res/values/strings.xml b/k9mail/src/main/res/values/strings.xml
index 5d93436b2e46732fce0964d62e507117d0efaebb..375c086d9b44babb31e633a7f365be3fc2a49757 100644
--- a/k9mail/src/main/res/values/strings.xml
+++ b/k9mail/src/main/res/values/strings.xml
@@ -1200,6 +1200,7 @@ Please submit bug reports, contribute new features and ask questions at
     <string name="messageview_crypto_warning_expired">This message was signed by an <b>expired key!</b></string>
     <string name="messageview_crypto_warning_insecure">This message was signed by an <b>insecure key!</b></string>
     <string name="messageview_crypto_warning_error">There was an <b>error in this message\'s signature!</b></string>
+    <string name="messageview_crypto_warning_unsigned">This message was encrypted, but not signed. It is <b>not end-to-end secure</b>!</string>
     <string name="recipient_error_non_ascii">Special characters are currently not supported!</string>
     <string name="recipient_error_parse_failed">Error parsing address!</string>
     <string name="account_settings_crypto_support_sign_only">Support signing of unencrypted messages</string>