diff --git a/src/main/java/eu/siacs/conversations/entities/Message.java b/src/main/java/eu/siacs/conversations/entities/Message.java
index b5a1897d..8cb48635 100644
--- a/src/main/java/eu/siacs/conversations/entities/Message.java
+++ b/src/main/java/eu/siacs/conversations/entities/Message.java
@@ -395,7 +395,7 @@ public class Message extends AbstractEntity {
 			String[] pathParts = url.getPath().split("/");
 			String filename;
 			if (pathParts.length > 0) {
-				filename = pathParts[pathParts.length - 1];
+				filename = pathParts[pathParts.length - 1].toLowerCase();
 			} else {
 				return false;
 			}
diff --git a/src/main/java/eu/siacs/conversations/http/HttpConnection.java b/src/main/java/eu/siacs/conversations/http/HttpConnection.java
index 5348e395..b715c3f3 100644
--- a/src/main/java/eu/siacs/conversations/http/HttpConnection.java
+++ b/src/main/java/eu/siacs/conversations/http/HttpConnection.java
@@ -65,7 +65,7 @@ public class HttpConnection implements Downloadable {
 		this.message.setDownloadable(this);
 		try {
 			mUrl = new URL(message.getBody());
-			String path = mUrl.getPath();
+			String path = mUrl.getPath().toLowerCase();
 			if (path != null && (path.endsWith(".pgp") || path.endsWith(".gpg"))) {
 				this.message.setEncryption(Message.ENCRYPTION_PGP);
 			} else if (message.getEncryption() != Message.ENCRYPTION_OTR) {
diff --git a/src/main/java/eu/siacs/conversations/xmpp/jingle/JingleConnection.java b/src/main/java/eu/siacs/conversations/xmpp/jingle/JingleConnection.java
index d6f901d8..ff94563c 100644
--- a/src/main/java/eu/siacs/conversations/xmpp/jingle/JingleConnection.java
+++ b/src/main/java/eu/siacs/conversations/xmpp/jingle/JingleConnection.java
@@ -280,7 +280,7 @@ public class JingleConnection implements Downloadable {
 			Element fileNameElement = fileOffer.findChild("name");
 			if (fileNameElement != null) {
 				String[] filename = fileNameElement.getContent()
-						.toLowerCase(Locale.US).split("\\.");
+						.toLowerCase(Locale.US).toLowerCase().split("\\.");
 				if (Arrays.asList(VALID_IMAGE_EXTENSIONS).contains(
 						filename[filename.length - 1])) {
 					message.setType(Message.TYPE_IMAGE);