diff --git a/phpseclib/File/ASN1.php b/phpseclib/File/ASN1.php
index f5a752c1..b9810b89 100644
--- a/phpseclib/File/ASN1.php
+++ b/phpseclib/File/ASN1.php
@@ -44,7 +44,7 @@
 /**
  * Include Math_BigInteger
  */
-include('Math/BigInteger.php');
+require_once('Math/BigInteger.php');
 
 /**#@+
  * Tag Classes
diff --git a/phpseclib/File/X509.php b/phpseclib/File/X509.php
index 57674516..df6e40cd 100644
--- a/phpseclib/File/X509.php
+++ b/phpseclib/File/X509.php
@@ -47,7 +47,7 @@
 /**
  * Include File_ASN1
  */
-include('File/ASN1.php');
+require_once('File/ASN1.php');
 
 /**
  * Flag to only accept signatures signed by certificate authorities