diff --git a/app/src/processing/app/AbstractTextMonitor.java b/app/src/processing/app/AbstractTextMonitor.java
index fdfcfba760a..b6e196a16b5 100644
--- a/app/src/processing/app/AbstractTextMonitor.java
+++ b/app/src/processing/app/AbstractTextMonitor.java
@@ -43,13 +43,10 @@ public abstract class AbstractTextMonitor extends AbstractMonitor {
   protected JComboBox lineEndings;
   protected JComboBox serialRates;
 
-  private SimpleDateFormat logDateFormat;
-  
   public AbstractTextMonitor(BoardPort boardPort) {
     super(boardPort);
-    logDateFormat = new SimpleDateFormat("HH:mm:ss.SSS -> ");
   }
-  
+
   protected void onCreateWindow(Container mainPane) {
     Font consoleFont = Theme.getFont("console.font");
     Font editorFont = PreferencesData.getFont("editor.font");
@@ -57,7 +54,7 @@ protected void onCreateWindow(Container mainPane) {
 
     mainPane.setLayout(new BorderLayout());
 
-    textArea = new TextAreaFIFO(8000000);
+    textArea = new TextAreaFIFO(8_000_000);
     textArea.setRows(16);
     textArea.setColumns(40);
     textArea.setEditable(false);
@@ -70,7 +67,7 @@ protected void onCreateWindow(Container mainPane) {
     scrollPane = new JScrollPane(textArea);
 
     mainPane.add(scrollPane, BorderLayout.CENTER);
-  
+
     JPanel upperPane = new JPanel();
     upperPane.setLayout(new BoxLayout(upperPane, BoxLayout.X_AXIS));
     upperPane.setBorder(new EmptyBorder(4, 4, 4, 4));
@@ -165,7 +162,7 @@ public void onSendCommand(ActionListener listener) {
     textField.addActionListener(listener);
     sendButton.addActionListener(listener);
   }
-  
+
   public void onClearCommand(ActionListener listener) {
     clearButton.addActionListener(listener);
   }
@@ -173,41 +170,38 @@ public void onClearCommand(ActionListener listener) {
   public void onSerialRateChange(ActionListener listener) {
     serialRates.addActionListener(listener);
   }
-  
-  public void message(final String s) {
-    SwingUtilities.invokeLater(new Runnable() {
-      // Pre-allocate all objects used for streaming data
-      Date t = new Date();
-      String now;
-      StringBuilder out = new StringBuilder(16384);
-      boolean isStartingLine = false;
-
-      public void run() {
-        if (addTimeStampBox.isSelected()) {
-          t.setTime(System.currentTimeMillis());
-          now = logDateFormat.format(t);
-          out.setLength(0);
-
-          StringTokenizer tokenizer = new StringTokenizer(s, "\n", true);
-          while (tokenizer.hasMoreTokens()) {
-            if (isStartingLine) {
-              out.append(now);
-            }
-            String token = tokenizer.nextToken();
-            out.append(token);
-            // tokenizer returns "\n" as a single token
-            isStartingLine = token.charAt(0) == '\n';
-          }
-
-          textArea.append(out.toString());
-        } else {
-          textArea.append(s);
-        }
-
-        if (autoscrollBox.isSelected()) {
-          textArea.setCaretPosition(textArea.getDocument().getLength());
-        }
+
+  public void message(String msg) {
+    SwingUtilities.invokeLater(() -> updateTextArea(msg));
+  }
+
+  private static final String LINE_SEPARATOR = "\n";
+  private boolean isStartingLine = true;
+
+  protected void updateTextArea(String msg) {
+    if (addTimeStampBox.isSelected()) {
+      textArea.append(addTimestamps(msg));
+    } else {
+      textArea.append(msg);
+    }
+    if (autoscrollBox.isSelected()) {
+      textArea.setCaretPosition(textArea.getDocument().getLength());
+    }
+  }
+
+  private String addTimestamps(String text) {
+    String now = new SimpleDateFormat("HH:mm:ss.SSS -> ").format(new Date());
+    final StringBuilder sb = new StringBuilder(text.length() + now.length());
+    StringTokenizer tokenizer = new StringTokenizer(text, LINE_SEPARATOR, true);
+    while (tokenizer.hasMoreTokens()) {
+      if (isStartingLine) {
+        sb.append(now);
       }
-    });
+      String token = tokenizer.nextToken();
+      sb.append(token);
+      // tokenizer returns "\n" as a single token
+      isStartingLine = token.equals(LINE_SEPARATOR);
+    }
+    return sb.toString();
   }
 }
diff --git a/app/test/processing/app/UpdateTextAreaActionTest.java b/app/test/processing/app/UpdateTextAreaActionTest.java
new file mode 100644
index 00000000000..b32ea1850be
--- /dev/null
+++ b/app/test/processing/app/UpdateTextAreaActionTest.java
@@ -0,0 +1,91 @@
+package processing.app;
+
+import static org.fest.assertions.Assertions.assertThat;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import cc.arduino.packages.BoardPort;
+import processing.app.helpers.PreferencesMap;
+
+public class UpdateTextAreaActionTest {
+
+  private static final String TIMESTAMP_REGEX = "\\d\\d:\\d\\d:\\d\\d.\\d\\d\\d";
+
+  class DummyTextMonitor extends AbstractTextMonitor {
+    public DummyTextMonitor(BoardPort boardPort) {
+      super(boardPort);
+    }
+  }
+
+  @Before
+  public void setup() {
+    PreferencesData.defaults = new PreferencesMap();
+    PreferencesData.set("editor.font", "Monospaced,plain,12");
+    PreferencesData.set("gui.scale", "100");
+    Theme.defaults = new PreferencesMap();
+    Theme.table.put("console.font", "Monospaced,plain,12");
+  }
+
+  @Test
+  public void noTimestampAdded() {
+    DummyTextMonitor textMon = new DummyTextMonitor(new BoardPort());
+    textMon.addTimeStampBox.setSelected(false);
+
+    textMon.updateTextArea("line1\nline2\r\nline3");
+    assertThat(textMon.textArea.getText()).matches("line1\nline2\r\nline3");
+  }
+
+  @Test
+  public void all3LinesHaveTimestampAdded() {
+    DummyTextMonitor textMon = new DummyTextMonitor(new BoardPort());
+    textMon.addTimeStampBox.setSelected(true);
+
+    textMon.updateTextArea("line1\nline2\r\nline3");
+    assertThat(textMon.textArea.getText())
+        .matches(TIMESTAMP_REGEX + " -> line1\\n" + //
+                 TIMESTAMP_REGEX + " -> line2\\r\\n" + //
+                 TIMESTAMP_REGEX + " -> line3");
+  }
+
+  @Test
+  public void emptyLinesHaveTimestampToo() {
+    DummyTextMonitor textMon = new DummyTextMonitor(new BoardPort());
+    textMon.addTimeStampBox.setSelected(true);
+
+    textMon.updateTextArea("line_1\n\nline_2");
+    assertThat(textMon.textArea.getText())
+        .matches(TIMESTAMP_REGEX + " -> line_1\\n" + //
+                 TIMESTAMP_REGEX + " -> \\n" + //
+                 TIMESTAMP_REGEX + " -> line_2");
+  }
+
+  @Test
+  public void newLinesAreRememberedWhenNewBufferIsUsed() {
+    DummyTextMonitor textMon = new DummyTextMonitor(new BoardPort());
+    textMon.addTimeStampBox.setSelected(true);
+
+    textMon.updateTextArea("no newline");
+    assertThat(textMon.textArea.getText())
+        .matches(TIMESTAMP_REGEX + " -> no newline");
+
+    textMon.updateTextArea(" more text");
+    assertThat(textMon.textArea.getText())
+        .matches(TIMESTAMP_REGEX + " -> no newline more text");
+
+    textMon.updateTextArea("\n");
+    assertThat(textMon.textArea.getText())
+        .matches(TIMESTAMP_REGEX + " -> no newline more text\n");
+
+    textMon.updateTextArea("\n");
+    assertThat(textMon.textArea.getText())
+        .matches(TIMESTAMP_REGEX + " -> no newline more text\n" + //
+                 TIMESTAMP_REGEX + " -> \n");
+
+    textMon.updateTextArea("third line");
+    assertThat(textMon.textArea.getText())
+        .matches(TIMESTAMP_REGEX + " -> no newline more text\n" + //
+                 TIMESTAMP_REGEX + " -> \n" + //
+                 TIMESTAMP_REGEX + " -> third line");
+  }
+}
\ No newline at end of file