diff --git a/algods/algods.py b/algods/algods.py
index 213736b..de8c06d 100644
--- a/algods/algods.py
+++ b/algods/algods.py
@@ -137,4 +137,8 @@ def parse(stream, similarity: float, display_tqdm: bool = False) -> None:
 
 def main():
     ns = parse_args()
+
+    if not (0 < ns.similarity <= 1):
+        raise ValueError(f"Invalid similiarity value: {ns.similarity}")
+
     parse(ns.input, ns.similarity, ns.progress)