diff --git a/app/src/processing/app/Base.java b/app/src/processing/app/Base.java
index 7af728fdd..34193e07d 100644
--- a/app/src/processing/app/Base.java
+++ b/app/src/processing/app/Base.java
@@ -1494,6 +1494,10 @@ public class Base {
         if (platformLabel == null)
           platformLabel = targetPackage.getId() + "-" + targetPlatform.getId();
 
+        // add an hint that this core lives in sketchbook
+        if (targetPlatform.isInSketchbook())
+          platformLabel += " (in sketchbook)";
+
         JMenu platformBoardsMenu = new JMenu(platformLabel);
         MenuScroller.setScrollerFor(platformBoardsMenu);
         platformMenus.add(platformBoardsMenu);
diff --git a/arduino-core/src/processing/app/debug/LegacyTargetPlatform.java b/arduino-core/src/processing/app/debug/LegacyTargetPlatform.java
index c00378c48..ad1030b8f 100644
--- a/arduino-core/src/processing/app/debug/LegacyTargetPlatform.java
+++ b/arduino-core/src/processing/app/debug/LegacyTargetPlatform.java
@@ -245,4 +245,9 @@ public class LegacyTargetPlatform implements TargetPlatform {
       res += "  " + boardId + " = " + boards.get(boardId) + "\n";
     return res + "}";
   }
+
+  @Override
+  public boolean isInSketchbook() {
+	return getFolder().getAbsolutePath().startsWith(BaseNoGui.getDefaultSketchbookFolder().getAbsolutePath());
+  }
 }
diff --git a/arduino-core/src/processing/app/debug/TargetPlatform.java b/arduino-core/src/processing/app/debug/TargetPlatform.java
index 4b13cf87a..330b260bb 100644
--- a/arduino-core/src/processing/app/debug/TargetPlatform.java
+++ b/arduino-core/src/processing/app/debug/TargetPlatform.java
@@ -94,4 +94,10 @@ public interface TargetPlatform {
    */
   public TargetPackage getContainerPackage();
 
+  /**
+   * Returns true if the platform is installed in a subfolder of the sketchbook
+   *
+   * @return
+   */
+  public boolean isInSketchbook();
 }