diff --git a/comic_download/comic_strip.py b/comic_download/comic_strip.py
index 9db0cd7..f77bd0b 100644
--- a/comic_download/comic_strip.py
+++ b/comic_download/comic_strip.py
@@ -79,7 +79,7 @@ def get_identifier_string(identifier):
         return identifier
     elif type(identifier) == tuple or type(identifier) == list:
         # Check for spaces. Their presence influenced the delimiter string.
-        if any(re.search(r'\s', id) for id in identifier):
+        if any(re.search(r'\s', str(id)) for id in identifier):
             delimiter = ' - '
         else:
             delimiter = '-'
@@ -100,6 +100,12 @@ class ImageRepo(ABC):
     seperately.
     """
 
+    download_headers = {
+        "accept-language": "en-US,en;q=0.9",
+        "dnt": "1",
+        "user-agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"
+    }
+
     def __init__(self, identifier, image_type):
         """
         Creates an information repository
@@ -249,7 +255,7 @@ class ImageRepo(ABC):
             for name in iterator:
                 logging.info("    Downloading repository %s resource %s", self.get_identifier_string(), name)
                 image_path = NamedTemporaryFile(mode='wb', suffix=str(name), prefix=self.get_identifier_string(), delete = False)
-                result = requests.get(self.image_urls[name])
+                result = requests.get(self.image_urls[name], headers=self.download_headers)
                 result.raise_for_status()
                 image_path.write(result.content)
                 image_path.close()
@@ -330,8 +336,8 @@ class Comic(ImageRepo, ABC):
         """
         with self._index_lock:
             if not self.identifier in self.strip_index:
-                self.strip_index[self.identifier] = {}
-            self.strip_index[self.identifier][strip.identifier] = strip.get_filename()
+                self.strip_index[self.get_identifier_string()] = {}
+            self.strip_index[self.get_identifier_string()][strip.identifier] = strip.get_filename()
 
     def is_strip_present(self, base_path: Path, suffix: str, identifier) -> bool:
         """
@@ -342,11 +348,11 @@ class Comic(ImageRepo, ABC):
         :param identifier: The identifier to check.
         :returns: True if the strip file has been saved.
         """
-        if not self.identifier in self.strip_index:
+        if not self.get_identifier_string() in self.strip_index:
             return False
-        if not identifier in self.strip_index[self.identifier]:
+        if not identifier in self.strip_index[self.get_identifier_string()]:
             return False
-        path = Path(base_path, self.strip_index[self.identifier][identifier] + suffix)
+        path = Path(base_path, self.strip_index[self.get_identifier_string()][identifier] + suffix)
         return path.exists()