diff --git a/cryptography/hazmat/bindings/openssl/cms.py b/cryptography/hazmat/bindings/openssl/cms.py
index a3760f2..cbf4b28 100644
--- a/cryptography/hazmat/bindings/openssl/cms.py
+++ b/cryptography/hazmat/bindings/openssl/cms.py
@@ -15,8 +15,8 @@
 
 INCLUDES = """
 #if !defined(OPENSSL_NO_CMS) && OPENSSL_VERSION_NUMBER >= 0x0090808fL
-// The next define should really be in the OpenSSL header, but it is missing.
-// Failing to include this on Windows causes compilation failures.
+/* The next define should really be in the OpenSSL header, but it is missing.
+   Failing to include this on Windows causes compilation failures. */
 #if defined(OPENSSL_SYS_WINDOWS)
 #include <windows.h>
 #endif