diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpDecryptVerifyOperation.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpDecryptVerifyOperation.java
index 43555e281..b9bac2307 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpDecryptVerifyOperation.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpDecryptVerifyOperation.java
@@ -390,7 +390,10 @@ public class PgpDecryptVerifyOperation extends BaseOperation<PgpDecryptVerifyInp
         } else {
             // try to guess from file ending
             String extension = MimeTypeMap.getFileExtensionFromUrl(originalFilename);
-            if (extension != null) {
+            if (TextUtils.isEmpty(extension) && originalFilename.contains(".")) {
+                extension = originalFilename.substring(originalFilename.lastIndexOf(".") +1);
+            }
+            if (!TextUtils.isEmpty(extension)) {
                 MimeTypeMap mime = MimeTypeMap.getSingleton();
                 mimeType = mime.getMimeTypeFromExtension(extension);
             }