diff --git a/arduino-core/src/cc/arduino/Compiler.java b/arduino-core/src/cc/arduino/Compiler.java
index d1aa1f2bdce..a220f784ad3 100644
--- a/arduino-core/src/cc/arduino/Compiler.java
+++ b/arduino-core/src/cc/arduino/Compiler.java
@@ -49,8 +49,10 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.nio.file.StandardCopyOption;
+import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.regex.Pattern;
@@ -249,6 +251,18 @@ private void callArduinoBuilder(TargetBoard board, TargetPlatform platform, Targ
     addPathFlagIfPathExists(cmd, "-built-in-libraries", BaseNoGui.getContentFile("libraries"));
     addPathFlagIfPathExists(cmd, "-libraries", BaseNoGui.getSketchbookLibrariesFolder().folder);
 
+    // adding several additional library directories, taken from preferences.txt
+    // additional_library_directories=path1[;path2[;...]]
+    Collection<String> additional_library_directories = splitAndTrim(PreferencesData.get("additional_library_directories"), ";");
+    for (String path : additional_library_directories) {
+	File fpath = new File(path);
+	addPathFlagIfPathExists(cmd, "-libraries", fpath);
+
+	if (!fpath.isDirectory()) {
+	    System.err.println(I18n.format(tr("Warning: additional_library_directories: directory '{0}' not found"), path));
+	}
+    }
+
     String fqbn = Stream.of(aPackage.getId(), platform.getId(), board.getId(), boardOptions(board)).filter(s -> !s.isEmpty()).collect(Collectors.joining(":"));
     cmd.add("-fqbn=" + fqbn);
 
@@ -623,4 +637,13 @@ private RunnerException placeException(String message, String fileName, int line
     }
     return null;
   }
+
+  private Collection<String> splitAndTrim(String text, String separator) {
+    if ((text == null) || (text.length() == 0)) {
+      return Collections.emptyList() ;
+    }
+
+    Collection<String> parts = Arrays.asList(text.split(separator));
+    return parts.stream().map(String::trim).filter(part -> !part.isEmpty()).collect(Collectors.toList());
+  }
 }
diff --git a/arduino-core/src/processing/app/BaseNoGui.java b/arduino-core/src/processing/app/BaseNoGui.java
index 0dfbd4ccc74..d64948b4016 100644
--- a/arduino-core/src/processing/app/BaseNoGui.java
+++ b/arduino-core/src/processing/app/BaseNoGui.java
@@ -33,6 +33,7 @@
 import java.util.*;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+import java.util.stream.Collectors;
 
 import cc.arduino.packages.BoardPort;
 
@@ -672,6 +673,19 @@ static public void onBoardOrPortChange() {
     // Add libraries folder for the sketchbook
     librariesFolders.add(getSketchbookLibrariesFolder());
 
+    // Adding several additional library directories, taken from preferences.txt
+    // additional_library_directories=path1[;path2[;...]]
+    Collection<String> additional_library_directories = splitAndTrim(PreferencesData.get("additional_library_directories"), ";");
+    for (String path : additional_library_directories) {
+       File fpath = new File(path);
+
+       if (fpath.isDirectory()) {
+	   librariesFolders.add(new UserLibraryFolder(fpath, Location.ADDITIONAL));
+       } else {
+           System.err.println(I18n.format(tr("Warning: additional_library_directories: directory '{0}' not found"), path));
+       }
+    }
+
     // Scan for libraries in each library folder.
     // Libraries located in the latest folders on the list can override
     // other libraries with the same name.
@@ -949,6 +963,15 @@ static public void showError(String title, String message, Throwable e) {
     notifier.showError(title, message, e, 1);
   }
 
+  static private Collection<String> splitAndTrim(String text, String separator) {
+    if ((text == null) || (text.length() == 0)) {
+      return Collections.emptyList() ;
+    }
+
+    Collection<String> parts = Arrays.asList(text.split(separator));
+    return parts.stream().map(String::trim).filter(part -> !part.isEmpty()).collect(Collectors.toList());
+  }
+
   /**
    * Show an error message that's actually fatal to the program.
    * This is an error that can't be recovered. Use showWarning()
diff --git a/arduino-core/src/processing/app/packages/UserLibraryFolder.java b/arduino-core/src/processing/app/packages/UserLibraryFolder.java
index 53371a21323..f181132f8e0 100644
--- a/arduino-core/src/processing/app/packages/UserLibraryFolder.java
+++ b/arduino-core/src/processing/app/packages/UserLibraryFolder.java
@@ -34,7 +34,7 @@
 public class UserLibraryFolder {
 
   public enum Location {
-    SKETCHBOOK, CORE, REFERENCED_CORE, IDE_BUILTIN,
+    SKETCHBOOK, CORE, REFERENCED_CORE, IDE_BUILTIN, ADDITIONAL,
   }
 
   public File folder;
diff --git a/arduino-core/src/processing/app/packages/UserLibraryPriorityComparator.java b/arduino-core/src/processing/app/packages/UserLibraryPriorityComparator.java
index fe64ba1aa6e..1f6cf84c605 100644
--- a/arduino-core/src/processing/app/packages/UserLibraryPriorityComparator.java
+++ b/arduino-core/src/processing/app/packages/UserLibraryPriorityComparator.java
@@ -38,7 +38,8 @@ public class UserLibraryPriorityComparator implements Comparator<UserLibrary> {
 
   private final static Map<Location, Integer> priorities = new HashMap<>();
   static {
-    priorities.put(Location.SKETCHBOOK, 4);
+    priorities.put(Location.SKETCHBOOK, 5);
+    priorities.put(Location.ADDITIONAL, 4);
     priorities.put(Location.CORE, 3);
     priorities.put(Location.REFERENCED_CORE, 2);
     priorities.put(Location.IDE_BUILTIN, 1);