diff --git a/searches/binary_search.py b/searches/binary_search.py
index 6bab1c1cbdc5..11a51e38c7eb 100644
--- a/searches/binary_search.py
+++ b/searches/binary_search.py
@@ -49,6 +49,9 @@ def bisect_left(
     >>> bisect_left([1, 2, 2, 2, 4], 2)
     1
     """
+    if lo < 0:
+        raise ValueError("lo must be non-negative")
+
     if hi < 0:
         hi = len(sorted_collection)
 
@@ -96,6 +99,9 @@ def bisect_right(
     >>> bisect_right([1, 2, 2, 2, 4], 2)
     4
     """
+    if lo < 0:
+        raise ValueError("lo must be non-negative")
+
     if hi < 0:
         hi = len(sorted_collection)