diff --git a/app/src/processing/app/Base.java b/app/src/processing/app/Base.java
index 7f177f829..19429e2c7 100644
--- a/app/src/processing/app/Base.java
+++ b/app/src/processing/app/Base.java
@@ -29,6 +29,7 @@ import java.util.*;
 import java.util.List;
 
 import javax.swing.*;
+import javax.swing.filechooser.FileNameExtensionFilter;
 
 import processing.app.debug.TargetPackage;
 import processing.app.debug.TargetPlatform;
@@ -2611,6 +2612,7 @@ public class Base {
     JFileChooser fileChooser = new JFileChooser(System.getProperty("user.home"));
     fileChooser.setDialogTitle(_("Select a zip file or a folder containing the library you'd like to add"));
     fileChooser.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
+    fileChooser.setFileFilter(new FileNameExtensionFilter("ZIP files or folders", "zip"));
 
     Dimension preferredSize = fileChooser.getPreferredSize();
     fileChooser.setPreferredSize(new Dimension(preferredSize.width + 200, preferredSize.height + 200));
@@ -2657,7 +2659,7 @@ public class Base {
       // copy folder
       File destinationFolder = new File(getSketchbookLibrariesFolder(), sourceFile.getName());
       if (!destinationFolder.mkdir()) {
-        editor.statusError("Can't create folder: " + sourceFile.getName() + " into libraries folder");
+        editor.statusError("A library named " + sourceFile.getName() + " already exists");
         return;
       }
       try {