diff --git a/arduino-core/src/cc/arduino/contributions/DownloadableContribution.java b/arduino-core/src/cc/arduino/contributions/DownloadableContribution.java
index 531ad5b3dc9..87ef9cee465 100644
--- a/arduino-core/src/cc/arduino/contributions/DownloadableContribution.java
+++ b/arduino-core/src/cc/arduino/contributions/DownloadableContribution.java
@@ -32,6 +32,7 @@
 import com.github.zafarkhaja.semver.Version;
 
 import java.io.File;
+import java.util.Optional;
 
 public abstract class DownloadableContribution {
 
@@ -66,10 +67,10 @@ public void setDownloadedFile(File downloadedFile) {
   }
 
   public String getParsedVersion() {
-    Version version = VersionHelper.valueOf(getVersion());
-    if (version == null) {
-      return null;
+    Optional<Version> version = VersionHelper.valueOf(getVersion());
+    if (version.isPresent()) {
+      return version.get().toString();
     }
-    return version.toString();
+    return null;
   }
 }
diff --git a/arduino-core/src/cc/arduino/contributions/VersionComparator.java b/arduino-core/src/cc/arduino/contributions/VersionComparator.java
index ccdca994091..ba0ebb639c7 100644
--- a/arduino-core/src/cc/arduino/contributions/VersionComparator.java
+++ b/arduino-core/src/cc/arduino/contributions/VersionComparator.java
@@ -34,41 +34,32 @@
 import cc.arduino.contributions.libraries.ContributedLibrary;
 
 import java.util.Comparator;
+import java.util.Optional;
 
 public class VersionComparator implements Comparator<String> {
 
-  @Override
-  public int compare(String a, String b) {
-    // null is always less than any other value
-    if (a == null && b == null)
-      return 0;
-    if (a == null)
-      return -1;
-    if (b == null)
-      return 1;
-
-    Version versionA = VersionHelper.valueOf(a);
-    Version versionB = VersionHelper.valueOf(b);
-
-    return versionA.compareTo(versionB);
-  }
-
-  public static boolean greaterThan(String a, String b) {
-    // null is always less than any other value
-    if (a == null && b == null) {
-      return false;
+  public static int compareTo(String a, String b) {
+    Optional<Version> versionA = VersionHelper.valueOf(a);
+    Optional<Version> versionB = VersionHelper.valueOf(b);
+    if (versionA.isPresent() && versionB.isPresent()) {
+      return versionA.get().compareTo(versionB.get());
     }
-    if (a == null) {
-      return false;
+    if (versionA.isPresent()) {
+      return 1;
     }
-    if (b == null) {
-      return true;
+    if (versionB.isPresent()) {
+      return -1;
     }
+    return 0;
+  }
 
-    Version versionA = VersionHelper.valueOf(a);
-    Version versionB = VersionHelper.valueOf(b);
+  @Override
+  public int compare(String a, String b) {
+    return compareTo(a, b);
+  }
 
-    return versionA.greaterThan(versionB);
+  public static boolean greaterThan(String a, String b) {
+    return compareTo(a, b) > 0;
   }
 
   public static String max(String a, String b) {
@@ -79,8 +70,7 @@ public static ContributedLibrary max(ContributedLibrary a, ContributedLibrary b)
     return greaterThan(a, b) ? a : b;
   }
 
-  public static boolean greaterThan(ContributedLibrary a,
-                                    ContributedLibrary b) {
+  public static boolean greaterThan(ContributedLibrary a, ContributedLibrary b) {
     return greaterThan(a.getParsedVersion(), b.getParsedVersion());
   }
 }
diff --git a/arduino-core/src/cc/arduino/contributions/VersionHelper.java b/arduino-core/src/cc/arduino/contributions/VersionHelper.java
index 0f108aed5a7..caf98c8f120 100644
--- a/arduino-core/src/cc/arduino/contributions/VersionHelper.java
+++ b/arduino-core/src/cc/arduino/contributions/VersionHelper.java
@@ -29,13 +29,15 @@
 
 package cc.arduino.contributions;
 
+import java.util.Optional;
+
 import com.github.zafarkhaja.semver.Version;
 
 public class VersionHelper {
 
-  public static Version valueOf(String ver) {
+  public static Optional<Version> valueOf(String ver) {
     if (ver == null) {
-      return null;
+      return Optional.empty();
     }
     try {
       // Allow x.y-something, assuming x.y.0-something
@@ -49,7 +51,7 @@ public static Version valueOf(String ver) {
       }
       String[] parts = version.split("\\.");
       if (parts.length >= 3) {
-        return Version.valueOf(ver);
+        return Optional.of(Version.valueOf(ver));
       }
       if (parts.length == 2) {
         version += ".0";
@@ -57,10 +59,9 @@ public static Version valueOf(String ver) {
       if (parts.length == 1) {
         version += ".0.0";
       }
-      return Version.valueOf(version + extra);
+      return Optional.of(Version.valueOf(version + extra));
     } catch (Exception e) {
-      System.err.println("Invalid version found: " + ver);
-      return null;
+      return Optional.empty();
     }
   }
 
diff --git a/arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java b/arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java
index 4193b2ba088..8b7acae748c 100644
--- a/arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java
+++ b/arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java
@@ -54,6 +54,7 @@
 import java.util.List;
 import java.util.Optional;
 
+import static processing.app.I18n.format;
 import static processing.app.I18n.tr;
 
 public class LibrariesIndexer {
@@ -203,7 +204,7 @@ private void scanLibrary(UserLibraryFolder folderDesc) throws IOException {
       LegacyUserLibrary lib = LegacyUserLibrary.create(folderDesc);
       String[] headers = BaseNoGui.headerListFromIncludePath(lib.getSrcFolder());
       if (headers.length == 0) {
-        throw new IOException(lib.getSrcFolder().getAbsolutePath());
+        throw new IOException(format(tr("no headers files (.h) found in {0}"), lib.getSrcFolder()));
       }
       addToInstalledLibraries(lib);
       return;
@@ -213,7 +214,7 @@ private void scanLibrary(UserLibraryFolder folderDesc) throws IOException {
     UserLibrary lib = UserLibrary.create(folderDesc);
     String[] headers = BaseNoGui.headerListFromIncludePath(lib.getSrcFolder());
     if (headers.length == 0) {
-      throw new IOException(lib.getSrcFolder().getAbsolutePath());
+      throw new IOException(format(tr("no headers files (.h) found in {0}"), lib.getSrcFolder()));
     }
     addToInstalledLibraries(lib);
 
diff --git a/arduino-core/src/processing/app/packages/UserLibrary.java b/arduino-core/src/processing/app/packages/UserLibrary.java
index ee9c0bd031b..e22ae36eb29 100644
--- a/arduino-core/src/processing/app/packages/UserLibrary.java
+++ b/arduino-core/src/processing/app/packages/UserLibrary.java
@@ -28,11 +28,8 @@
  */
 package processing.app.packages;
 
-import cc.arduino.Constants;
-import cc.arduino.contributions.VersionHelper;
-import cc.arduino.contributions.libraries.ContributedLibraryReference;
-import processing.app.helpers.PreferencesMap;
-import processing.app.packages.UserLibraryFolder.Location;
+import static processing.app.I18n.format;
+import static processing.app.I18n.tr;
 
 import java.io.File;
 import java.io.IOException;
@@ -41,9 +38,16 @@
 import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Optional;
 
 import com.github.zafarkhaja.semver.Version;
 
+import cc.arduino.Constants;
+import cc.arduino.contributions.VersionHelper;
+import cc.arduino.contributions.libraries.ContributedLibraryReference;
+import processing.app.helpers.PreferencesMap;
+import processing.app.packages.UserLibraryFolder.Location;
+
 public class UserLibrary {
 
   private String name;
@@ -148,12 +152,16 @@ public static UserLibrary create(UserLibraryFolder libFolderDesc) throws IOExcep
     }
 
     String declaredVersion = properties.get("version").trim();
-    Version version = VersionHelper.valueOf(declaredVersion);
+    Optional<Version> version = VersionHelper.valueOf(declaredVersion);
+    if (!version.isPresent()) {
+      System.out.println(
+          format(tr("Invalid version '{0}' for library in: {1}"), declaredVersion, libFolder.getAbsolutePath()));
+    }
 
     UserLibrary res = new UserLibrary();
     res.installedFolder = libFolder;
     res.name = properties.get("name").trim();
-    res.version = version.toString();
+    res.version = version.isPresent() ? version.get().toString() : declaredVersion;
     res.author = properties.get("author").trim();
     res.maintainer = properties.get("maintainer").trim();
     res.sentence = properties.get("sentence").trim();