diff --git a/lib/widgets/markdown_toolbar.dart b/lib/widgets/markdown_toolbar.dart
index 4446c8c8..127be37d 100644
--- a/lib/widgets/markdown_toolbar.dart
+++ b/lib/widgets/markdown_toolbar.dart
@@ -98,6 +98,8 @@ TextEditingValue modifyCurrentLine(
   var lineStartPos = text.lastIndexOf('\n', cursorPos == 0 ? 0 : cursorPos - 1);
   if (lineStartPos == -1) {
     lineStartPos = 0;
+  } else {
+    lineStartPos += 1;
   }
 
   var lineEndPos = text.indexOf('\n', cursorPos);
diff --git a/test/markdown_toolbar_test.dart b/test/markdown_toolbar_test.dart
index 36533ec1..de73218f 100644
--- a/test/markdown_toolbar_test.dart
+++ b/test/markdown_toolbar_test.dart
@@ -17,4 +17,55 @@ void main() {
 
     expect(modifyCurrentLine(val, '# '), expectedVal);
   });
+
+  test('Adds a header to the last line correctly', () {
+    var val = const TextEditingValue(
+      text: 'Hi\nHello',
+      selection: TextSelection.collapsed(offset: 8),
+    );
+
+    var expectedVal = const TextEditingValue(
+      text: 'Hi\n# Hello',
+      selection: TextSelection.collapsed(offset: 10),
+    );
+
+    expect(modifyCurrentLine(val, '# '), expectedVal);
+  });
+
+  test('Adds a header to a middle line correctly', () {
+    var val = const TextEditingValue(
+      text: 'Hi\nHello\nFire',
+      selection: TextSelection.collapsed(offset: 8),
+    );
+
+    var expectedVal = const TextEditingValue(
+      text: 'Hi\n# Hello\nFire',
+      selection: TextSelection.collapsed(offset: 10),
+    );
+
+    expect(modifyCurrentLine(val, '# '), expectedVal);
+  });
+
+  test('Adds a header to a middle line middle word correctly', () {
+    var val = const TextEditingValue(
+      text: 'Hi\nHello Darkness\nFire',
+      selection: TextSelection.collapsed(offset: 8),
+    );
+
+    var expectedVal = const TextEditingValue(
+      text: 'Hi\n# Hello Darkness\nFire',
+      selection: TextSelection.collapsed(offset: 10),
+    );
+
+    expect(modifyCurrentLine(val, '# '), expectedVal);
+  });
+
+  // Removes from first line
+  // Removes from last line
+  // Removes from middle line
+  // Removes when cursor is in the middle of a word
+  // Removes when cursor is at the start of the line
+  // Removes when cursor is in between '#' and ' '
+
+  // TODO: Simplify the tests, avoid all this code duplication
 }