diff --git a/cs50/2017/fall/vigenere/check50/__init__.py b/cs50/2017/fall/vigenere/check50/__init__.py
index 6f18799..b27eb51 100644
--- a/cs50/2017/fall/vigenere/check50/__init__.py
+++ b/cs50/2017/fall/vigenere/check50/__init__.py
@@ -11,7 +11,7 @@ def exists(self):
     @check("exists")
     def compiles(self):
         """vigenere.c compiles."""
-        self.spawn("clang -o vigenere vigenere.c -lcs50 -lm").exit(0)
+        self.spawn("clang -o vigenere vigenere.c -lcs50 -lm -std=c11").exit(0)
 
     @check("compiles")
     def aa(self):