diff --git a/library/x509.c b/library/x509.c
index 88e75c1..92e52c3 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -468,7 +468,7 @@
 }
 
 #define snprintf compat_snprintf
-#endif
+#endif /* _MSC_VER && !snprintf && !EFIX64 && !EFI32 */
 
 #define POLARSSL_ERR_DEBUG_BUF_TOO_SMALL    -2
 
@@ -652,7 +652,7 @@
     now->hour = lt.tm_hour;
     now->min = lt.tm_min;
     now->sec = lt.tm_sec;
-#endif
+#endif /* _WIN32 && !EFIX64 && !EFI32 */
 }
 
 /*
@@ -796,9 +796,9 @@
 #else
     ((void) verbose);
     return( POLARSSL_ERR_X509_FEATURE_UNAVAILABLE );
-#endif
+#endif /* POLARSSL_CERTS_C && POLARSSL_SHA1_C */
 }
 
-#endif
+#endif /* POLARSSL_SELF_TEST */
 
 #endif /* POLARSSL_X509_USE_C */