diff --git a/src/main/java/eu/siacs/conversations/entities/Downloadable.java b/src/main/java/eu/siacs/conversations/entities/Downloadable.java
index c32165e8..8fae91bb 100644
--- a/src/main/java/eu/siacs/conversations/entities/Downloadable.java
+++ b/src/main/java/eu/siacs/conversations/entities/Downloadable.java
@@ -4,6 +4,7 @@ public interface Downloadable {
 
 	String[] VALID_IMAGE_EXTENSIONS = {"webp", "jpeg", "jpg", "png", "jpe"};
 	String[] VALID_CRYPTO_EXTENSIONS = {"pgp", "gpg", "otr"};
+	String[] WELL_KNOWN_EXTENSIONS = {"pdf","m4a"};
 
 	int STATUS_UNKNOWN = 0x200;
 	int STATUS_CHECKING = 0x201;
@@ -14,6 +15,7 @@ public interface Downloadable {
 	int STATUS_OFFER_CHECK_FILESIZE = 0x206;
 	int STATUS_UPLOADING = 0x207;
 
+
 	boolean start();
 
 	int getStatus();
diff --git a/src/main/java/eu/siacs/conversations/entities/Message.java b/src/main/java/eu/siacs/conversations/entities/Message.java
index d15f3bbd..ac5a9d56 100644
--- a/src/main/java/eu/siacs/conversations/entities/Message.java
+++ b/src/main/java/eu/siacs/conversations/entities/Message.java
@@ -497,7 +497,8 @@ public class Message extends AbstractEntity {
 				} else {
 					return Decision.NEVER;
 				}
-			} else if (Arrays.asList(Downloadable.VALID_IMAGE_EXTENSIONS).contains(extension)) {
+			} else if (Arrays.asList(Downloadable.VALID_IMAGE_EXTENSIONS).contains(extension)
+					|| Arrays.asList(Downloadable.WELL_KNOWN_EXTENSIONS).contains(extension)) {
 				return Decision.SHOULD;
 			} else {
 				return Decision.NEVER;