diff --git a/CHANGELOG.md b/CHANGELOG.md
index ef5808a..af5b50d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+# v1.0.7 (pre-release)
+- Ignore chapter markers and single newlines when calculating text length.
+
 # v1.0.6
 - Added `Insert chapter marker` button in text editor to insert chapter markers at the current cursor position.
 - Added `Preview` button in voice mixer to preview the voice mix with the selected settings.
diff --git a/abogen/gui.py b/abogen/gui.py
index 401a096..97e2a11 100644
--- a/abogen/gui.py
+++ b/abogen/gui.py
@@ -386,8 +386,14 @@ class TextboxDialog(QDialog):
         return self.text_edit.toPlainText()
 
     def handle_ok(self):
+        text = self.text_edit.toPlainText()
+        # Check if text is empty based on character count
+        if calculate_text_length(text) == 0:
+            QMessageBox.warning(self, "Textbox Error", "Text cannot be empty.")
+            return
+
         # If the text hasn't changed, treat as cancel
-        if self.text_edit.toPlainText() == self.original_text:
+        if text == self.original_text:
             self.reject()
         else:
             # Check if we need to warn about overwriting a non-temporary file
diff --git a/abogen/utils.py b/abogen/utils.py
index 1ea9dd8..58aab35 100644
--- a/abogen/utils.py
+++ b/abogen/utils.py
@@ -119,8 +119,10 @@ def save_config(config):
 
 
 def calculate_text_length(text):
-    # Remove double newlines (replace them with single newlines)
-    cleaned_text = text.replace("\n\n", "")
+    # Ignore chapter markers
+    text_no_markers = re.sub(r"<<CHAPTER_MARKER:.*?>>", "", text)
+    # Ignore newlines
+    cleaned_text = text_no_markers.replace("\n", "")
     # Calculate character count
     char_count = len(cleaned_text)
     return char_count