diff --git a/arduino-core/src/cc/arduino/contributions/packages/ContributionsIndexer.java b/arduino-core/src/cc/arduino/contributions/packages/ContributionsIndexer.java
index 64d0a41ed..50e67fb38 100644
--- a/arduino-core/src/cc/arduino/contributions/packages/ContributionsIndexer.java
+++ b/arduino-core/src/cc/arduino/contributions/packages/ContributionsIndexer.java
@@ -75,7 +75,7 @@ public class ContributionsIndexer {
     }
     index = parseIndex(defaultIndexFile);
 
-    File[] indexFiles = preferencesFolder.listFiles(new PackageIndexFilenameFilter(Constants.DEFAULT_INDEX_FILE_NAME));
+    File[] indexFiles = preferencesFolder.listFiles(new TestPackageIndexFilenameFilter(new PackageIndexFilenameFilter(Constants.DEFAULT_INDEX_FILE_NAME)));
 
     for (File indexFile : indexFiles) {
       ContributionsIndex contributionsIndex = parseIndex(indexFile);
diff --git a/arduino-core/src/cc/arduino/contributions/packages/PackageIndexFilenameFilter.java b/arduino-core/src/cc/arduino/contributions/packages/PackageIndexFilenameFilter.java
index 22c777305..61e7c2663 100644
--- a/arduino-core/src/cc/arduino/contributions/packages/PackageIndexFilenameFilter.java
+++ b/arduino-core/src/cc/arduino/contributions/packages/PackageIndexFilenameFilter.java
@@ -13,6 +13,6 @@ public class PackageIndexFilenameFilter implements FilenameFilter {
 
   @Override
   public boolean accept(File file, String name) {
-    return !defaultPackageIndexFileName.equals(name) && name.startsWith("package_") && name.endsWith("_index.json");
+    return new File(file, name).isFile() && !defaultPackageIndexFileName.equals(name) && name.startsWith("package_") && name.endsWith("_index.json");
   }
 }
diff --git a/arduino-core/src/cc/arduino/contributions/packages/TestPackageIndexFilenameFilter.java b/arduino-core/src/cc/arduino/contributions/packages/TestPackageIndexFilenameFilter.java
new file mode 100644
index 000000000..6d134eb77
--- /dev/null
+++ b/arduino-core/src/cc/arduino/contributions/packages/TestPackageIndexFilenameFilter.java
@@ -0,0 +1,27 @@
+package cc.arduino.contributions.packages;
+
+import java.io.File;
+import java.io.FilenameFilter;
+
+public class TestPackageIndexFilenameFilter implements FilenameFilter {
+
+  private final FilenameFilter parent;
+
+  public TestPackageIndexFilenameFilter(FilenameFilter parent) {
+    this.parent = parent;
+  }
+
+  public TestPackageIndexFilenameFilter() {
+    this(null);
+  }
+
+  @Override
+  public boolean accept(File file, String name) {
+    boolean result = false;
+    if (parent != null) {
+      result = parent.accept(file, name);
+    }
+    result = result || (new File(file, name).isFile() && name.startsWith("test_package_") && name.endsWith("_index.json"));
+    return result;
+  }
+}