diff --git a/src/kex.c b/src/kex.c
index f05008b0..2e963bbb 100644
--- a/src/kex.c
+++ b/src/kex.c
@@ -42,24 +42,28 @@
 # define AES "aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,"
 # define DES "3des-cbc"
 # define DES_SUPPORTED "3des-cbc,des-cbc-ssh1"
+
 #elif defined(HAVE_LIBCRYPTO)
+
 # ifdef HAVE_OPENSSL_BLOWFISH_H
 #  define BLOWFISH "blowfish-cbc,"
-# else
+# else /* HAVE_OPENSSL_BLOWFISH_H */
 #  define BLOWFISH ""
-# endif
+# endif /* HAVE_OPENSSL_BLOWFISH_H */
+
 # ifdef HAVE_OPENSSL_AES_H
 #  ifdef BROKEN_AES_CTR
 #   define AES "aes256-cbc,aes192-cbc,aes128-cbc,"
-#  else
+#  else /* BROKEN_AES_CTR */
 #   define AES "aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,"
 #  endif /* BROKEN_AES_CTR */
-# else
+# else /* HAVE_OPENSSL_AES_H */
 #  define AES ""
-#  endif
+# endif /* HAVE_OPENSSL_AES_H */
+
 # define DES "3des-cbc"
 # define DES_SUPPORTED "3des-cbc,des-cbc-ssh1"
-#endif
+#endif /* HAVE_LIBCRYPTO */
 
 #ifdef WITH_ZLIB
 #define ZLIB "none,zlib,zlib@openssh.com"