diff --git a/app.py b/app.py
index 16d6cb6..e80df6e 100644
--- a/app.py
+++ b/app.py
@@ -1101,24 +1101,70 @@ def _replace_or_append_option(content, directive, new_block):
     Handles:
       - brace-delimited:  'forwarders { ... };'  /  'allow-recursion { ... };'
       - value-terminated: 'dnssec-validation auto;'  /  'recursion yes;'
-    Nested braces are matched by counting depth.
+    Nested braces are matched by counting depth. Comments ('//', '#', '/*...*/')
+    are skipped so the directive name doesn't match inside comment text.
     """
+    # Build a mask of which character ranges are inside comments. We treat the
+    # whole file linearly:
+    #   - '//' to end-of-line: line comment (BIND and shell style)
+    #   - '#' to end-of-line: line comment (BIND 9.18+ accepts # too)
+    #   - '/* ... */': block comment
+    n = len(content)
+    in_comment = [False] * n  # True at position i = i is inside a comment
+
+    i = 0
+    while i < n:
+        c = content[i]
+        # End of block comment
+        if in_comment[i] is False and i + 1 < n and c == '/' and content[i + 1] == '*':
+            j = i + 2
+            depth = 1
+            while j < n and depth > 0:
+                if j + 1 < n and content[j] == '*' and content[j + 1] == '/':
+                    depth -= 1
+                    j += 2
+                else:
+                    j += 1
+            for k in range(i, j):
+                in_comment[k] = True
+            i = j
+            continue
+        # Line comment // ... \n
+        if in_comment[i] is False and i + 1 < n and c == '/' and content[i + 1] == '/':
+            j = i
+            while j < n and content[j] != '\n':
+                in_comment[j] = True
+                j += 1
+            i = j
+            continue
+        # Line comment # ... \n (skip only if at start of token; be conservative
+        # and treat any '#' preceded by whitespace or start-of-line as a comment)
+        if in_comment[i] is False and c == '#':
+            # Only treat as comment if preceded by whitespace or start-of-line
+            prev_ok = (i == 0) or content[i - 1] in ' \t'
+            if prev_ok:
+                j = i
+                while j < n and content[j] != '\n':
+                    in_comment[j] = True
+                    j += 1
+                i = j
+                continue
+        i += 1
+
     pattern = re.compile(
-        r'(?<!\w)(?<!\-)(' + re.escape(directive) + r')\b(?!\w)(?!\-)',
-        re.MULTILINE,
+        r'(?<!\w)(?<!-)(' + re.escape(directive) + r')\b(?!-)(?!\w)',
     )
 
     for m in pattern.finditer(content):
-        # Skip lines where the directive is part of a longer hyphenated name,
-        # e.g. don't match 'recursion' when looking for it inside 'allow-recursion'.
-        # The negative lookbehind `(?<!\-)` and lookahead `(?!\-)` together cover
-        # both directions. Belt-and-suspenders: also check next char isn't '-'.
+        start = m.start()
+        # Skip if this match is inside a comment
+        if in_comment[start]:
+            continue
         end_kw = m.end()
         if end_kw < len(content) and content[end_kw] == '-':
             continue
 
-        start = m.start()
-        # Detect indentation by looking at whitespace before the directive
+        # Detect indentation
         line_start = content.rfind('\n', 0, start) + 1
         indent = ''
         for ch in content[line_start:start]:
@@ -1127,18 +1173,19 @@ def _replace_or_append_option(content, directive, new_block):
             else:
                 break
 
-        # Look ahead: is this a brace-delimited directive or value-terminated?
+        # Look ahead: brace-delimited or value-terminated?
         i = end_kw
-        # Skip whitespace
         while i < len(content) and content[i] in ' \t':
             i += 1
         if i >= len(content):
             continue
 
         if content[i] == '{':
-            # Brace-delimited: walk forward to matching `};`
             depth = 0
             for j in range(i, len(content)):
+                # Skip over comments inside the brace body
+                if in_comment[j]:
+                    continue
                 c = content[j]
                 if c == '{':
                     depth += 1
@@ -1155,20 +1202,18 @@ def _replace_or_append_option(content, directive, new_block):
                             for line in new_block.split('\n')
                         )
                         return content[:start] + indented + content[end:]
-            continue  # malformed, try next match
+            continue
         else:
-            # Value-terminated: read tokens up to `;`
             end = i
             while end < len(content) and content[end] != ';':
                 end += 1
             if end < len(content):
-                end += 1  # consume the `;`
+                end += 1
             indented = '\n'.join(
                 (indent + line) if line else line
                 for line in new_block.split('\n')
             )
             return content[:start] + indented + content[end:]
-        # else: malformed, try next match
 
     # Not found — append after the opening "options {" line
     opt_match = re.search(r'options\s*\{', content)
@@ -1180,7 +1225,6 @@ def _replace_or_append_option(content, directive, new_block):
         indented = '\n'.join('    ' + line if line else line for line in new_block.split('\n'))
         indented = '\n' + indented + '\n'
         return content[:insert_at] + indented + content[insert_at:]
-    # No options block — create one
     return 'options {\n' + new_block + '\n};\n'