diff --git a/Doc/library/concurrent.futures.rst b/Doc/library/concurrent.futures.rst
index 47ca6b38f84eee..3890e49f597b77 100644
--- a/Doc/library/concurrent.futures.rst
+++ b/Doc/library/concurrent.futures.rst
@@ -257,6 +257,10 @@ ProcessPoolExecutor Example
        1099726899285419]
 
    def is_prime(n):
+       if n < 2:
+           return False
+       if n == 2:
+           return True
        if n % 2 == 0:
            return False