diff --git a/tiktoken/load.py b/tiktoken/load.py
index 3c76bcb3..ba94630a 100644
--- a/tiktoken/load.py
+++ b/tiktoken/load.py
@@ -63,6 +63,12 @@ def read_file_cached(blobpath: str, expected_hash: str | None = None) -> bytes:
         except OSError:
             pass
 
+    if os.environ.get("TIKTOKEN_OFFLINE"):
+        raise ValueError(
+            f"TIKTOKEN_OFFLINE is set but the file {blobpath} is not in the cache at {cache_dir}. "
+            f"Please download it first or set TIKTOKEN_CACHE_DIR to a directory containing the file."
+        )
+
     contents = read_file(blobpath)
     if expected_hash and not check_hash(contents, expected_hash):
         raise ValueError(
@@ -107,7 +113,9 @@ def data_gym_to_mergeable_bpe_ranks(
 
     # vocab_bpe contains the merges along with associated ranks
     vocab_bpe_contents = read_file_cached(vocab_bpe_file, vocab_bpe_hash).decode()
-    bpe_merges = [tuple(merge_str.split()) for merge_str in vocab_bpe_contents.split("\n")[1:-1]]
+    bpe_merges = [
+        tuple(merge_str.split()) for merge_str in vocab_bpe_contents.split("\n")[1:-1]
+    ]
 
     def decode_data_gym(value: str) -> bytes:
         return bytes(data_gym_byte_to_byte[b] for b in value)
@@ -156,7 +164,9 @@ def dump_tiktoken_bpe(bpe_ranks: dict[bytes, int], tiktoken_bpe_file: str) -> No
             f.write(base64.b64encode(token) + b" " + str(rank).encode() + b"\n")
 
 
-def load_tiktoken_bpe(tiktoken_bpe_file: str, expected_hash: str | None = None) -> dict[bytes, int]:
+def load_tiktoken_bpe(
+    tiktoken_bpe_file: str, expected_hash: str | None = None
+) -> dict[bytes, int]:
     # NB: do not add caching to this function
     contents = read_file_cached(tiktoken_bpe_file, expected_hash)
     ret = {}
@@ -167,5 +177,7 @@ def load_tiktoken_bpe(tiktoken_bpe_file: str, expected_hash: str | None = None)
             token, rank = line.split()
             ret[base64.b64decode(token)] = int(rank)
         except Exception as e:
-            raise ValueError(f"Error parsing line {line!r} in {tiktoken_bpe_file}") from e
+            raise ValueError(
+                f"Error parsing line {line!r} in {tiktoken_bpe_file}"
+            ) from e
     return ret