diff --git a/src/CacheLibrary/CacheLibrary.py b/src/CacheLibrary/CacheLibrary.py
index 89b3b5b..2d48b3e 100644
--- a/src/CacheLibrary/CacheLibrary.py
+++ b/src/CacheLibrary/CacheLibrary.py
@@ -102,6 +102,10 @@ def __init__(
 
         path = Path(file_path)
 
+        if path.is_dir():
+            msg = f"Cache file path must be a file. '{path.resolve().as_posix()}' is a directory."
+            raise ValueError(msg)
+
         if path.suffix == ".json":
             self.cache_file = JsonCacheFile(
                 path,