diff --git a/arduino-core/src/cc/arduino/contributions/packages/DownloadableContributionsDownloader.java b/arduino-core/src/cc/arduino/contributions/packages/DownloadableContributionsDownloader.java
index 1a963254b30..2b8898619c4 100644
--- a/arduino-core/src/cc/arduino/contributions/packages/DownloadableContributionsDownloader.java
+++ b/arduino-core/src/cc/arduino/contributions/packages/DownloadableContributionsDownloader.java
@@ -57,17 +57,18 @@ public File download(DownloadableContribution contribution,
     // Ensure the existence of staging folder
     stagingFolder.mkdirs();
 
-    // Need to download or resume downloading?
-    if (!outputFile.isFile() || (outputFile.length() < contribution.getSize())) {
-      download(url, outputFile, progress, statusText);
+    if (fileAlreadyDownloaded(outputFile, contribution)) {
+      contribution.setDownloaded(true);
+      contribution.setDownloadedFile(outputFile);
+      return outputFile;
     }
 
+    download(url, outputFile, progress, statusText);
+
     // Test checksum
     progress.setStatus(_("Verifying archive integrity..."));
     onProgress(progress);
-    String checksum = contribution.getChecksum();
-    String algo = checksum.split(":")[0];
-    if (!FileHash.hash(outputFile, algo).equals(checksum)) {
+    if (checksumMatches(outputFile, contribution)) {
       throw new Exception(_("CRC doesn't match. File is corrupted."));
     }
 
@@ -76,6 +77,29 @@ public File download(DownloadableContribution contribution,
     return outputFile;
   }
 
+  private boolean checksumMatches(File outputFile,
+                                  DownloadableContribution contribution)
+      throws Exception {
+    final String checksum = contribution.getChecksum();
+    final String algo = checksum.split(":")[0];
+
+    return FileHash.hash(outputFile, algo).equals(checksum);
+  }
+
+  private boolean fileAlreadyDownloaded
+      (File outputFile,
+       DownloadableContribution contribution) throws Exception {
+    if (!outputFile.isFile()) {
+      return false;
+    }
+
+    if (outputFile.length() != contribution.getSize()) {
+      return false;
+    }
+
+    return checksumMatches(outputFile, contribution);
+  }
+
   public void download(URL url, File tmpFile, final Progress progress,
                        final String statusText) throws Exception {
     FileDownloader downloader = new FileDownloader(url, tmpFile);