diff --git a/app/src/processing/app/SketchController.java b/app/src/processing/app/SketchController.java
index 89f1a35167f..392422c5923 100644
--- a/app/src/processing/app/SketchController.java
+++ b/app/src/processing/app/SketchController.java
@@ -709,6 +709,10 @@ private boolean upload(String suggestedClassName, boolean usingProgrammer) throw
 
     UploaderUtils uploaderInstance = new UploaderUtils();
     Uploader uploader = uploaderInstance.getUploaderByPreferences(false);
+    if (uploader == null) {
+      editor.statusError(tr("Please select a Port before Upload"));
+      return false;
+    }
 
     EditorConsole.setCurrentEditorConsole(editor.console);
 
diff --git a/arduino-core/src/cc/arduino/UploaderUtils.java b/arduino-core/src/cc/arduino/UploaderUtils.java
index ec27b496148..108d7c137b3 100644
--- a/arduino-core/src/cc/arduino/UploaderUtils.java
+++ b/arduino-core/src/cc/arduino/UploaderUtils.java
@@ -50,7 +50,11 @@ public Uploader getUploaderByPreferences(boolean noUploadPort) {
 
     BoardPort boardPort = null;
     if (!noUploadPort) {
-      boardPort = BaseNoGui.getDiscoveryManager().find(PreferencesData.get("serial.port"));
+      String port = PreferencesData.get("serial.port");
+      if (port == null || port.isEmpty()) {
+        return null;
+      }
+      boardPort = BaseNoGui.getDiscoveryManager().find(port);
     }
 
     return new UploaderFactory().newUploader(target.getBoards().get(board), boardPort, noUploadPort);
diff --git a/build/shared/lib/preferences.txt b/build/shared/lib/preferences.txt
index e777627af3d..7e7fd7c381c 100644
--- a/build/shared/lib/preferences.txt
+++ b/build/shared/lib/preferences.txt
@@ -267,7 +267,8 @@ programmer = arduino:avrispmkii
 upload.using = bootloader
 upload.verify = true
 
-serial.port=COM1
+#default port is empty to prevent running AVRDUDE before Port selected (issue #7943)
+serial.port=
 serial.databits=8
 serial.stopbits=1
 serial.parity=N