diff --git a/library/x509_crt.c b/library/x509_crt.c
index d7723ac..0a22b87 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -986,7 +986,8 @@
         ret = POLARSSL_ERR_X509_FILE_IO_ERROR;
 
     FindClose( hFind );
-#else
+#else /* _WIN32 */
+#if defined(POLARSSL_HAVE_READDIR_R)
     int t_ret, i;
     struct stat sb;
     struct dirent entry, *result = NULL;
@@ -1023,7 +1024,12 @@
             ret += t_ret;
     }
     closedir( dir );
-#endif
+#else /* POLARSSL_HAVE_READDIR_R */
+    ((void) chain);
+    ((void) path);
+    ret = POLARSSL_ERR_X509_FEATURE_UNAVAILABLE;
+#endif /* POLARSSL_HAVE_READDIR_R */
+#endif /* _WIN32 */
 
     return( ret );
 }