diff --git a/src/androidTest/java/com/b44t/messenger/uitests/offline/SharingTest.java b/src/androidTest/java/com/b44t/messenger/uitests/offline/SharingTest.java
index bd92116b5..6759343c0 100644
--- a/src/androidTest/java/com/b44t/messenger/uitests/offline/SharingTest.java
+++ b/src/androidTest/java/com/b44t/messenger/uitests/offline/SharingTest.java
@@ -93,7 +93,7 @@ public class SharingTest {
       }
     }
     Uri uri = Uri.parse("content://" + BuildConfig.APPLICATION_ID + ".attachments/" + Uri.encode(pngImage));
-    DcHelper.sharedFiles.put(pngImage, 1);
+    DcHelper.sharedFiles.put(pngImage, "image/png");
 
     Intent i = new Intent(Intent.ACTION_SEND);
     i.setType("image/png");
diff --git a/src/main/java/org/thoughtcrime/securesms/connect/AttachmentsContentProvider.java b/src/main/java/org/thoughtcrime/securesms/connect/AttachmentsContentProvider.java
index 6471c0ea0..e03d805e5 100644
--- a/src/main/java/org/thoughtcrime/securesms/connect/AttachmentsContentProvider.java
+++ b/src/main/java/org/thoughtcrime/securesms/connect/AttachmentsContentProvider.java
@@ -5,9 +5,15 @@ import android.content.ContentValues;
 import android.database.Cursor;
 import android.net.Uri;
 import android.os.ParcelFileDescriptor;
+import android.webkit.MimeTypeMap;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 
 import com.b44t.messenger.DcContext;
 
+import org.thoughtcrime.securesms.util.MediaUtil;
+
 import java.io.File;
 import java.io.FileNotFoundException;
 
@@ -34,12 +40,12 @@ public class AttachmentsContentProvider extends ContentProvider {
         // where ef39a39 is the file in the blob directory
         // and text.txt is the original name of the file, as returned by `msg.getFilename()`.
         // `uri.getPathSegments()` returns ["ef39a39", "text.txt"] in this example.
-        String path = uri.getPathSegments().get(0);
-        if (!DcHelper.sharedFiles.containsKey(path)) {
+        String file = uri.getPathSegments().get(0);
+        if (!DcHelper.sharedFiles.containsKey(file)) {
             throw new FileNotFoundException("File was not shared before.");
         }
 
-        File privateFile = new File(dcContext.getBlobdir(), path);
+        File privateFile = new File(dcContext.getBlobdir(), file);
         return ParcelFileDescriptor.open(privateFile, ParcelFileDescriptor.MODE_READ_ONLY);
     }
 
@@ -49,8 +55,17 @@ public class AttachmentsContentProvider extends ContentProvider {
     }
 
     @Override
-    public String getType(Uri arg0) {
-        return null;
+    public String getType(Uri uri) {
+        String file = uri.getPathSegments().get(0);
+        String mimeType = DcHelper.sharedFiles.get(file);
+
+        return DcHelper.checkMime(uri.toString(), mimeType);
+    }
+
+    @Override
+    public String getTypeAnonymous(Uri uri) {
+        String ext = MediaUtil.getFileExtensionFromUrl(uri.toString());
+        return MimeTypeMap.getSingleton().getMimeTypeFromExtension(ext);
     }
 
     @Override
diff --git a/src/main/java/org/thoughtcrime/securesms/connect/DcHelper.java b/src/main/java/org/thoughtcrime/securesms/connect/DcHelper.java
index 5f1b37686..d09a5dfc6 100644
--- a/src/main/java/org/thoughtcrime/securesms/connect/DcHelper.java
+++ b/src/main/java/org/thoughtcrime/securesms/connect/DcHelper.java
@@ -266,7 +266,9 @@ public class DcHelper {
     return Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
   }
 
-  public static final HashMap<String, Integer> sharedFiles = new HashMap<>();
+  // When the user shares a file to another app or opens a file in another app, it is added here.
+  // `HashMap<file, mimetype>` where `file` is the name of the file in the blobdir (not the user-visible filename).
+  public static final HashMap<String, String> sharedFiles = new HashMap<>();
 
   public static void openForViewOrShare(Context activity, int msg_id, String cmd) {
     DcContext dcContext = getContext(activity);
@@ -291,12 +293,17 @@ public class DcHelper {
       }
 
       Uri uri;
+      mimeType = checkMime(filename, mimeType);
       if (path.startsWith(dcContext.getBlobdir())) {
         // Build a Uri that will later be passed to AttachmentsContentProvider.openFile().
         // The last part needs to be `filename`, i.e. the original, user-visible name of the file,
         // so that the external apps show the name of the file correctly.
         uri = Uri.parse("content://" + BuildConfig.APPLICATION_ID + ".attachments/" + Uri.encode(file.getName()) + "/" + Uri.encode(filename));
-        sharedFiles.put(file.getName(), 1); // as different Android version handle uris in putExtra differently, we also check them on our own
+
+        // As different Android version handle uris in putExtra differently,
+        // we also check on our own that the file was actually shared.
+        // The check happens in AttachmentsContentProvider.openFile().
+        sharedFiles.put(file.getName(), mimeType);
       } else {
         if (Build.VERSION.SDK_INT >= 24) {
           uri = FileProvider.getUriForFile(activity, BuildConfig.APPLICATION_ID + ".fileprovider", file);
@@ -306,7 +313,6 @@ public class DcHelper {
       }
 
       if (cmd.equals(Intent.ACTION_VIEW)) {
-        mimeType = checkMime(filename, mimeType);
         Intent intent = new Intent(Intent.ACTION_VIEW);
         intent.setDataAndType(uri, mimeType);
         intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
@@ -357,7 +363,7 @@ public class DcHelper {
     activity.startActivity(intent);
   }
 
-  private static String checkMime(String path, String mimeType) {
+  public static String checkMime(String path, String mimeType) {
     if(mimeType == null || mimeType.equals("application/octet-stream")) {
       path = path.replaceAll(" ", "");
       String extension = MediaUtil.getFileExtensionFromUrl(path);
diff --git a/src/main/res/values/strings.xml b/src/main/res/values/strings.xml
index 93ed533fb..084d19c21 100644
--- a/src/main/res/values/strings.xml
+++ b/src/main/res/values/strings.xml
@@ -503,6 +503,8 @@
     <string name="profile_encryption">Encryption</string>
     <string name="profile_shared_chats">Shared Chats</string>
     <string name="related_chats">Related Chats</string>
+    <!-- Separator between the list of actual members and past members -->
+    <string name="past_members">Past Members</string>
     <string name="tab_contact">Contact</string>
     <string name="tab_group">Group</string>
     <string name="tab_gallery">Gallery</string>